Hi, thanks for writing to HCM.
Based on the description, most propably it could be a scalp hematoma
If a scalp hematoma is caused by head trauma
and the child is not exhibiting any symptoms, then it is better to supervise and observe their behavior for a time to make sure that symptoms of brain trauma
do not appear.
Generally, these scalp hematomas needs no specific measures and it will resolve spontaneously, over time the hematoma and inflammation will reduce in size and become softer as the body breaks down the clot and remove the excess protective fluid.
A CT scan
and an xray may be needed to exclude any intracranial hemorrhage
Hope this information is helpful. Good day