Feeling stupid after hitting head but bad headache. Should I bother my gp for help?

Yes. Get checked out: your doctor can tell you if there is anything to be concerned about and you'll feel better knowing there is nothing wrong.
Concussion sxs. A bad headache could be a symptom of a concussion. Sxs of a concussion can include headache, nausea, vomiting, dizziness ringing in the ears or loss of balance. Bright lights may cause pain. Vision can blur or you may see bright colors. You may not think as clearly as normal. You can have a concussion with or without loss of consciousness. There can be memory problems, confusion or moodiness.