In addition to the good suggestions made by Chiron, you might also try coffee enemas for pain relief.
I had a similar problem for many months, which related back to falling on a slippery boat ramp and reaching out and saving myself by grabbing the crank handle on the trailer. It did some ligament damage and likely pinched a nerve or two. Eventually it got better but then flared up again some years later. I think one thing that helped me was a suggestion by a chiropractor friend to take time every so often to let my arms dangle and to do a bit or rotation of the shoulder without strainiing it and then a couple of times a day to lie on the bed with my upper part of my body hanging off (shoulders, neck and head) and just let my arms dangle free. Hard to say for sure, as I did take supplements such as fish oil (I now take krill oil) and glucosamine/chondroitin, hiyaluronic acid, silica, etc. But something worked. Now, if only something would work for my damnable back! Actually, it too is coming around - but for the most part it is physical therapy and spinal decompression.