Moderate pain in teen male. Near hip bone right side. Says he feels like its inside the hip bone. What could it be?

Hip, knee or ankle. Leg pain can often be referred up and down the leg. Hip pain can be caused by a problem with the hip, knee or ankle. In the case of a teen, it could be multiple things from simple strains and "growing pains" to more ominous things like legg-calve-perthes disease. In general, leg pain in kids should be evaluated by a physician.
Many things. If he has fever or vomiting call your doctor right away (appendicitis?). If he seems well, it is most likely a muscle sprain or bone bruise. If it persists, or he has an underlying disorder (like sickle cell or leukemia) see your doctor as soon as you can.