Have a pain in my left chest that won't go away what could it be?

Many causes: Left sided chest pain often is associated with cardiac disease. However musculoskeletal injury or inflammation involving rib or muscle can cause pain. Gastroesophageal reflux is probably the most common cause of chest pain. Other characteristics of pain including location, type, severity and duration are factors along with physical exam and testing would help your doctor determine etiology.

Chest wall/GERD/LUNG: At your age i will say the pain can be caused by following causes 1pain in the chest wall, when pain will be worse on movements, on touching, and deep breathing.Common inllammation called costochondritis, rib or chest wall bone disease etc 2esophageal reflux/esophagitis that is inflammation in esophagus 3 diseases of lungs and pleura 4heart disease if it is not getting better you should consult yourmd.