Thanks for writing.
Swelling of the scalp
is common after head injury
due to structure of the soft tissue in the scalp area. It usually takes few days to weeks for the swelling and accompanying pain to subside.
You should consult a Neurophysician if :-
1. Swelling or pain persists
2. Episode of nausea
4. Loss of memory
5. Difficulty in balancing of the body
According to the symptoms you have mentioned, it seems that there is soft tissue injury
which will heal by itself.
I hope this is helpful to you.