In most of the cases swelling following head injury
is due to hematoma
which occurs outside bone.
If following injury there is no irritability or abnormal behavior,no vomiting
or abnormal movement then there is no need to worry.
Just observe your child for her activity, oral intake, any vomiting or increase in size of swelling. If you find any abnormality consult your doctor immediately. Swelling usually subsides within 10-15 days on its own.