Thank you for your query,
The swelling is due to formation of hematoma
because of collection of blood in scalp layers above the skull bones.
Look for vomitings, altered behavior, decreased movements of the limbs and any fluid or blood leakage from nose or ears. If you find any abnormality consult Emergency immediately.
You can apply ice locally and give analgesic
in prescribed dosage for pain relief. And consult your Pediatrician
for physical examination and further medical advise.
Hope i have answered your query.