The pain could be due to gas, kidney stones, muscle pull, gall bladder stones, liver infection, constipation,
appendicitis or due to start of shingles. Duodenal
ulcer, IBS, Crohn’s disease and colitis are the other possibilities. It is difficult to comment beyond this at this stage without examining you. Also since you otherwise feel fine it could be gas or muscle pull. Still on net a confirmed diagnosis is not possible. Do consult your doctor. Take care!