Young, tall, healthy men who have smoked are at risk for a spontaneous pneumothorax. This is when the lung sacks just burst and leak a little air into the surrounding cavity. This is a common cause of the type of pain you are describing. You would need to be examined (and possibly X-rayed) to rule this out. Cancer in you case would be EXTREMELY unlikely. If you don t have a pneumothorax, then the most likely cause of your pain, as you suggest would be muscle spasm or an inflammation of the lining of the lung - pleurisy. Also, a rare but important cause of shoulder tip pain is pressure on the diaphragm. If you took a hit in hockey you could potentially have a small bleed in the liver or spleen can be felt in the shoulder tip. Sorry for the long list of possibilities, but if you came to my clinic, these would be the problems I would actively seek to diagnose and rule out. You should really get to your family doctor/walk-in clinic to sort this out as soon as possible.