Every child sooner or later strikes his head. Falls are especially common when your child is learning to walk. Most bruises occur on the forehead. Sometimes black eyes appear 3 days later because the bruising spreads downward by gravity. Most head trauma results simply in a scalp injury.
Big lumps can occur with minor injuries because the blood supply to the scalp is so plentiful.
For the same reason small cuts on the head may bleed profusely. Only 1 to 2 percent of injured children get a skull fracture. Usually there are no associated symptoms except for a headache at the site of impact. Your child has not had a concussion unless there is temporary unconsciousness, confusion, and amnesia. If there is a scrape, wash it off with soap and water.