Why do I have pain on the chest right hand side?

Many possibilities. Pain in any part of the chest could be from anything in or near the chest because of 'referred pain', a phenomenon of the very comples nervous system in human. So this pain may be from skin, muscle, rib/cartilage joint, esophagus, lining of lung (pleura), lining of heart (pericardium)--often sharp or stabbing quality; or heart--usually squeezing, pressure, elephant on chest pain. Check it out.