I had shoulder pain in my right arm since 10yrs now started in left arm after taking covid moderne shot after 15days not sure what it could be related how could i can get relief from pain its medium pain not too little or too high?

Do not attribute your symptoms to the vaccine, which causes local pain for about 3-4 days maximum. Rather, evaluate potential of shoulder joint pathology. Are there degenerative problems, or even rotator cuff tearing? See an orthopedic surgeon and consider imaging.

I am not certain that I understand what you have described. But if the pain in the left arm began 15 days after vaccination, it is not likely that this is the cause of the pain.