Go to the doctor. Explain where the pain is. Take the tests and find out.

The number of potential causes is legion; dislocated rib, torn cartilage, gall bladder, kidneys, liver, twisted colon, impending bowel blockage, calcification, translocated angina, tumor (cancerous, pre-cancerous, non-cancerous, takes your pick), spiral fracture, etc etc etc......

Doctor. NOW.