A slammed door can bring a scream and a rush of worry. Most of these injuries turn out to be bruises, but some involve the bone or the tissue under the nail, so it helps to know what to check.

Why It Happens and What Can Be Hurt

The fingertip has thin bone covered by the nail and the nail bed beneath it. A sudden crush can split the skin, rupture small vessels so blood collects under the nail, or crack the tip of the bone. Children’s hospital guidance on fingertip crush injuries notes that a cut nail bed may need stitches to prevent a deformed nail, and that a fracture in this area, though uncommon, is treated as an open fracture when the skin is broken and may need antibiotics.

How the Picture Differs

  • Simple bruise: swelling and discoloration, but the child can bend and straighten the finger, and pain tends to ease within a day or two.
  • Blood under the nail (subungual hematoma): dark red or black color under the nail with throbbing pain. When enough blood is trapped, a clinician may release the pressure through the nail.
  • Nail bed injury: torn skin beside the nail or a nail that is lifted needs evaluation.
  • Fracture: suspected when the finger looks bent, swelling is marked, the child cannot bend or straighten it, or pain lingers for a week or more. One pediatric emergency physician’s rule of thumb is that pain lasting a week or two suggests a break.

First Aid at Home

  • Cool the finger with cold water or a cloth-wrapped ice pack for 10 to 15 minutes to limit swelling and bleeding.
  • Raise the hand above heart level.
  • For pain, use acetaminophen or ibuprofen at the dose for the child’s weight; check with a pharmacist or pediatrician if unsure.
  • Press a clean gauze on any bleeding, then cover with a bandage. Remove rings before swelling begins.
  • Watch nail color, finger color, and feeling over the next few hours.

Common Misunderstandings

  • “If it moves, it isn’t broken.” A crack can still allow movement.
  • “Drain the blood under the nail with a pin at home.” This risks infection and further injury and is left to clinicians.
  • “A big bruise means a fracture.” Bruise size alone is a poor guide.

When to Seek Care

See a pediatrician or urgent care for an X-ray if the finger looks bent, cannot be bent or straightened, blood covers half or more of the nail, the nail is lifted, or the skin is split open. Go to the emergency room right away if the fingertip is cut off, bone is visible, bleeding does not stop with pressure, or the finger is pale or blue and numb. Spreading redness, pus, or fever in the following days can mean infection. This information is based on U.S. children’s hospital guidance; if you live elsewhere, check with a local pediatrician for country-specific advice. This information isn’t a diagnostic tool and doesn’t replace advice from a medical professional.