What do i do if i just got a tetanus shot and have a bad headache and itching on parts my body.?

See your doctor: Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.

Allergic reaction?: If you do not often get symptoms like these, except from the tetanus shot, i would recommend seeing your doctor asap. Sounds like it could be an allergic reaction. Also, was the tetanus shot given as a preventative measure, or did you have to get it because of some recent broken skin trauma? It could be from the trauma.