But I'll tell you what helped me 2 different times (once left shoulder, another time right, both climbing injuries, didn't properly warm-up) -- acupuncture. Sometimes once will do it (worked on pinched nerve in back before) but if more serious problems best to go once a week for about a month. Don't take this as medical advice, just something to consider before taking more serious measures.
That actually doen't surprise me at all, because there are times when it is really bad where I will take a hard rubber ball I bought (it's actually a dog toy lol) and put that under the back side of my shoulder while laying down for a bit and oddly enough that seems to take some of the pain away for a little bit. Guess it's somewhat of the same principal with pressure points.

