I have pain in one of my ribs. when i yawn or breathe in, a sharp pain occurs. what is wrong?

Many things: Pain in your ribs that is sharp when you breath could be a number of things. Among the less serious complaints would be a muscle spasm, costochondritis (an inflammation of the cartilage in your ribs) or a cracked or broken rib. Rib pain can also herald more ominous things as well. Definitely worth getting checked out with your doc.

Pleuritis: Is a general term for pain when taking a deep breath and can be caused by a number of things, including infections and inflammation. You should see your doctor about this to make sure it is not something serious. Anti-inflammatory drugs like Ibuprofen and naproxyn help with pleurisy. Costochondritis and trauma can also cause localised pain.