The pain in the left upper chest may be caused by the following reasons: 1, it may be caused by trauma to the chest, such as being injured by the chest to form a crush injury, which leads to the local soft tissue of the left upper chest to appear to have swelling, pain, generally have a clear history of trauma. 2, it may be the thoracic costochondritis of the left upper chest, it is the sterile inflammation of the cartilage between the sternum and the ribs, and it is usually found in the chest. There will be localized pressure and pain, and if the inflammation is strong, there will be localized redness, swelling and heat pain, and the pain will be aggravated during chest activities, such as deep breathing or chest exertion.3, there may be heart problems, acute heart disease, such as angina pectoris, myocardial infarction may cause pain, but it is usually accompanied by symptoms such as tightness in the chest, palpitations or pallor, weakness of limbs, cold sweat and so on. The symptoms of the disease include: chest tightness, palpitations, pale face, weakness of the limbs, cold sweats, and so on.