My 11 month old son knocked his head. after a day swelling started but no bruises. took him to the emergency room and the doctor said it's a hematoma but after 4 days swelling won't go down even if i put a ice pack on.

Headache, vomiting : If your son is otherwise well, the swelling will usually diminish within 7 days. Watch for signs of weakness, vision or hearing problems, moderate headache, trouble walking, vomiting. If these occur, please see the Emergency Department.

May need a recheck: Children often hit their heads. If a child is behaving differently after an injury, he can be evaluated by his pediatrician, or sometimes an emergency room visit is needed depending on the symptoms. If the swelling was not there after the impact but grew overnight, the question is whether or not there is slow bleeding on the inside of the skull. Several days out now, his pediatrician can recheck.