What should I do for pain? Hurt my wrist fighting, when I bend it backwards it hurts like a sharp quick pain until I put it back down

First . First of all I have to say you really should not be fighting. You could really hurt yourself or someone else and even end up in jail. Now on to your problem. It sounds like you sprained your wrist. You need to keep it immobilized. You can buy a wrist splint in any pharmacy. Ice it, rest it, and keep it elevated. Take advil (ibuprofen) or Ibuprofen for pain. If your wrist is very swollen or tender to the touch with severe pain then you might have a fracture (broken bone) and you will need medical attention right away. Take care and stay out of trouble. Happy new year.