Why is my nail black after I hit it?
Last updated September 3, 2026.
A black nail after a knock is blood trapped under the nail - a bruise in a sealed box. It will not turn pink again; a new nail grows from the base and pushes the damage out over about 6 months for a fingernail, up to 18 for a toenail. Fierce throbbing pressure can be drained by a clinician. Pymander is a free AI doctor, 24/7 by text, and can help you judge it.
What to do
- Ice and elevate right after the hit to limit the bleed.
- Severe throbbing pressure? See a clinician promptly - draining it is a two-minute job, not a DIY job.
- Let it grow out: trim loose edges, keep it clean, protect the nail bed.
- Redness, pus, fever, or a bent finger? Get it seen - infection and fractures change the plan.
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