My sternum is hurting, it hurts to cough or deep breath?

Sternum pain: I assume you haven't had an injury of your chestwall. Can you locate a tender area especially at the junction of the sternum and a rib which could be an inflamed joint. Sometimes the cause of chest pain on a deep breath or with a cough is a pinched intercostal nerve or muscle, pleurisy, early pneumonia or inflammation of the heart lining( pericarditis).. See a physician if the pain persists.