Black Toenail from Injury: Bruise, Healing, and When to See a Doctor

Last reviewed: 2026-08-06

Quick answer

A black toenail after running, hiking, or stubbing your toe is almost always a bruise under the nail, called a subungual hematoma. It happens when injury breaks small blood vessels beneath the nail and blood pools there. Most bruises grow out on their own over months and need no treatment, but see a doctor if the spot appeared without any injury, keeps growing, or spreads onto the skin beside the nail.

On this page

• What a black toenail from injury looks like
• Common causes
• Bruise or melanoma?
• Is it serious?
• What your body might be telling you
• What you can do
• FAQ

What it looks like

A bruised toenail looks like a dark patch under the nail, ranging from dark red or purple right after the injury to brown or black as the blood settles. Unlike the clean vertical line of nail pigment, an injury bruise is usually a blotch or an area of color, and it often matches the shape of whatever hit the toe.

Key detail: the bruise sits under the nail, and as the nail grows, the dark area moves forward toward the tip. That movement is one of the best signs that it is a healing bruise and nothing more.

Common causes

The name “runner’s toe” exists for a reason. Repetitive impact is the classic cause:

• Running or hiking in shoes that are too tight, especially downhill, where the toe repeatedly slams into the front of the shoe.
• Stubbing the toe on furniture, stairs, or curbs.
• Dropping something heavy on the foot.
• Sports with sudden stops and starts, like tennis, soccer, or basketball.
• Long-distance walking with poor footwear fit.

All of these share the same mechanism: force on the nail bed breaks tiny blood vessels, and blood collects under the nail plate.

Bruise or melanoma?

This is the question most people actually have, and the answer is reassuring for most readers: a bruise moves, melanoma grows.

• A bruise appears after a known injury (or after heavy training) and travels forward with the nail as it grows, usually fading or shedding at the tip within several months to a year.
• A concerning spot appears without any injury, does not move with nail growth, keeps growing or changing, or spreads pigment onto the skin around the nail.

That is why the injury history and a few weeks of watching matter. If the dark spot has no clear cause and is not tracking forward with the nail, a dermatologist should look at it. This article covers the injury version; the related guide on black lines on nails explains the pigment band version in more depth.

Is it serious?

Usually benign, monitor at home. A small to medium bruise from a clear injury, not very painful, with the dark area less than half of the nail. It will grow out over months.

Worth a medical look, not an emergency. A bruise covering more than half the nail, throbbing pain or pressure under the nail, or a nail that feels loose or partially detached.

See a doctor if:

• The dark spot appeared with no injury at all and you cannot explain it.
• The spot grows, changes shape, or does not move forward as the nail grows.
• Pigment spreads onto the skin beside or around the nail.
• Severe pain, or the toe looks bent or deformed, which can mean a fracture.
• Signs of infection appear: redness spreading, warmth, pus, or fever.
• You have diabetes or circulation problems, since foot injuries need more care.

For a large, painful bruise seen within the first day or two, a doctor can drain the trapped blood through a tiny hole in the nail, which relieves the pressure quickly.

What your body might be telling you

Straight answer: a black toenail from injury is trauma, not a nutrient message. No vitamin deficiency causes a bruise after stubbing your toe or running downhill, and no supplement will make the bruise heal faster.

The rare exceptions worth knowing:

• Very dark toenails with no injury history can, in uncommon cases, relate to something systemic, and are worth a doctor’s look rather than a supplement guess.
• Some sources note that B12 deficiency can darken nails in general, but that looks like diffuse pigment change, not a localized bruise, and it never follows an injury. If you are worried about B12, a blood test beats self-supplementing.

For most readers, the honest message is: your toe got bumped or your shoes are too tight. Fix the shoes, and let the nail grow.

What you can do

• Ice the toe early, 15 to 20 minutes at a time, to limit pain and swelling in the first day or two.
• Keep the nail clean and dry. A bruise is not an open wound, but a cracked nail can let infection in.
• Do not try to drain it yourself with a needle or blade. Infection risk is real, and a doctor can do it safely if needed.
• Trim the nail straight across and keep it short so it snags less, especially if it feels loose. Do not pull off a partially detached nail; let it separate on its own.
• Wear shoes with a roomy toe box, and keep toenails trimmed before long runs or hikes. Going up half a size or lacing to stop foot slide helps prevent repeat bruises.
• Track the spot with a photo every few weeks. If it moves toward the tip with the nail, that is healing. If it grows instead, that is a doctor visit.

FAQ

Is a black toenail from running dangerous? Almost never. It is a bruise under the nail from repeated impact, and it heals as the nail grows out. It only needs a check if it appeared with no injury, grows instead of moving forward, or spreads onto the skin around the nail.

How long does a bruised toenail take to heal? Toenails grow slowly, so the dark area can take several months to a year to grow out completely. In some cases the nail loosens and falls off on its own, and a new nail grows in behind it.

Should I drain a black toenail? Do not drain it yourself. For a large, painful bruise, a doctor can release the blood through a tiny hole in the nail within the first day or two, which eases the pressure. Small bruises do not need draining at all.

How can I tell a bruise from melanoma under the nail? Timing and movement: a bruise follows a known injury and travels forward with the nail as it grows. Melanoma does not move, tends to grow and change, and can spread pigment onto the skin beside the nail. No injury history plus a growing spot means a dermatologist should look.

My toenail turned black but I do not remember injuring it. What now? Worth a check. Many people forget minor stubs, but a dark spot with no clear cause that grows or does not move with the nail should be examined by a doctor, ideally a dermatologist, to rule out anything more serious.

Explore more: this guide is part of the complete library, what your nails say about your health.

Sources

• Cleveland Clinic: Subungual Hematoma, Bleeding and Bruising Under the Nail. https://my.clevelandclinic.org/health/diseases/subungual-hematoma
• Cleveland Clinic Health Essentials: What To Know About Runner’s Toe. https://health.clevelandclinic.org/how-to-prevent-and-treat-runners-toe
• U.S. Dermatology Partners: Toenail Bruise or Melanoma? Signs to Watch For. https://www.usdermatologypartners.com/blog/toenail-bruise-or-melanoma/
• Verywell Health: Signs You Need Treatment for Subungual Hematoma. https://www.verywellhealth.com/toenail-trauma-1337801

Disclaimer

This article is for information only and is not medical advice. Always consult a qualified healthcare provider about your health.

Reviewed by the VI Editorial Team. Last reviewed: August 6, 2026