I know everybody's different, but marijuana has always intensified my pain, especially with headaches and bone injuries.
Headaches were the worst though. If I had one of those little nagging headaches and fired up a joint, within 5 minutes I would feel like somebody whacked me in the head with a baseball bat.
The only thing weed has ever helped me with was nausea. That's it. Even then it was marginal - after a few tokes I could eat and hold my food down, but just barely. It never actually cured my nausea, just eased it a bit.