2-year-old baby fell behind the head a big bag often encountered, generally considered to be trauma caused by local capillary rupture, bleeding stasis blood gathered in the subcutaneous formation of local scalp hematoma, you need to immediately give the child a bag of local cold compresses, you can use a cool towel or ice compresses, can play a good role in stopping bleeding and swelling, to reduce the local exudate and seepage of blood. 48 hours later, you can use a hot water bag or hot towels to promote the dissipation and absorption of hematoma. After 48 hours, hot water bag or hot towel can be used to promote the dissipation of blood stasis and hematoma absorption, generally within 1 week the hematoma can be basically completely absorbed. Very few hematomas cannot be absorbed or even gradually increase in size, then it is necessary to puncture and extract the hematoma, and in severe cases, incision and drainage are needed. If your child has dizziness, headache or even nausea, vomiting, coma, etc. within 72 hours after the injury, you need to go to the hospital immediately for a cranial CT examination to determine whether there is a skull fracture or intracranial hemorrhage, and in serious cases, you need to be hospitalized immediately.