Thanks for writing your query.
After reading your post, it seems that you might have suffered from soft tissue injury
of the head.
Sometimes symptoms develop late i.e. after some time of the injury.
I would advise that you should go for a CT scan
. It will help to know if there is any skull injury or internal injury.
You should take complete rest in addition to the painkillers.
If the problem is persisting/increasing, you should immediately seek medical attention.
I hope this is helpful to you.