Pain over the left chest in patients with cough can be caused by many factors, including left lung inflammation, left intercostal neuralgia, and tension pneumothorax, as follows: 1. Left lung inflammation: More commonly, left lung inflammation is caused by the infection of some pathogens, such as viruses and bacteria. 2. Left intercostal neuralgia: It can be caused by inflammation of the left rib cage, resulting in left rib nerve pain, which is more obvious when coughing. 3. 3.Tension pneumothorax: In addition, it can also be seen in trauma, such as traffic accidents that cause fracture of the left rib cage, which punctures the pleural cavity and causes pneumothorax and elevated pressure, resulting in a right-sided tension pneumothorax and pain over the left chest when coughing. Usually, the diagnosis can be initially clarified through blood tests and CT of both lungs, and timely treatment can be provided.