Hi thanks for asking question. Here you are complaining pain in particular position esp.while turning to a side. So strong possibility is about moderate degree muscular strain.It might have occurred by heavy weight lift or during some activities.Simple analgesic taken.Take rest.Sleep in supine position . Second here costochondritis or rib fracture also has to be ruled out . Ribs are tender to touch.x ray also useful. If cough , cold , sore throat present then respiratory infections also has to be ruled out.treat it symptomatically.If still seems serious then x ray done for chest.CBC will also be done. If you have yellow sclera , right abdomen pain , anorexia then do your serum liver enzyme study for detecting liver pathology. Avoid stress as it can aggravate pain. I hope you will understand my concern. Dr.parth