Gall bladder stones and infection, duodenal ulcer and abscess under the right
diaphragm can cause referred pain
to right shoulder
. Anything that can cause pain
in the chest area, can cause pain in the shoulder area and the reverse is true too. Other than this the pain can be due to the joint itself.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into.