This probably sounds weird, but I hit my head when I'm frustrated.
That's not good. Why do you do that?
I like to displace my anger by punching myself
You really need to try and avoid hitting yourself in the head, as that could cause serious harm.  If this problem persists, I'd really suggest talking to a professional about it.
Nah, I'll be fine.
You need to find more constructive ways to deal with your frustrations. Banging your head could result in a concussion. You don't want to be injuring your brain -- it's the only one you've got.