This may be entirely unscientific, but I have had shoulder dystonia for quite a while and especially my right shoulder (my "good" side, thus the arm I use more) has been giving me problems. I try to stay warm, but when my muscles get too contracted and full of knots for whatever reason, one of the selfhelp remedies that works for me is to stretch those muscles by carrying weight on that side (tote a grocery bag from the store, walk around the house with a gallon milk jug or anything else at hand that's not too heavy).
Give it a try. If your pain gets worse, disregard this advice.