It won't be the heart itself if it hurts to breath in, unless there is excess fluid around the heart. Usually breathing in causing a pain is muscle associated and it's usually the muscles between the ribs. This can take a long time to resolve.
Sometimes TALL, young athletic men experience spontaneous collapse of a small part of the lung. You could also be experiencing pain from a pectoral muscle strain. It is unlikely the pain is heart related, otherwise it would be constant. If the pain persists or you experience shortness of breath go to the ER.