If you are worried just because you banged your head, then I would suggest it is probably not worth worrying about. People bang their heads, stub their toes and all sorts of other things all the time. These types of accidents are just that and nothing to worry about.
On the other hand, if the reason for banging your head was not accidental and you can pin it to something specific then you can further investigate that and take any necessary action. If this is something that is happening more often, it may be worth investigating, but otherwise worrying about banging your head is not something that will help you.
This subject (worries) is discussed oftentimes on this forum and so if I may, I will recycle one of the posts from not so long ago. Have a read and if you still feel you should worry, come back and see if you can tell us why exactly you are worried.
Take care|
P.S. Here is a PS ...
The below is from an article by NHS Borders
Share your worries
Worries do not survive well outside our heads. Talking about a
worry can help us to see the bigger picture and can help with
finding possible solutions or planning actions. Try and meet a
friend or relative and tell them what is on your mind. We all
worry and you can be sure they will also have things that they
worry about.