Injuries to a 17 year old male patient's foot after a bicycle accident. There is keloid scarring to the skin and blood under the big toenail. A keloid scar is a scar that fills with the protein collagen. In a normal scar the collagen breaks down once the wound has healed, but this fails to happen during the formation of a keloid scar. The scar expands from its original boundaries, and continues to grow even after the wound has healed. Blood under the nails, also known as a subungual haematoma, occurs when blood vessels beneath the nail rupture. In most cases the blood drains away after a few days, but occasionally it needs to be lanced and drained surgically.