Thanks for putting up your query over here. The type of pain and location you mentioned have following possibilities- It can be traumatic,so would like to ask you if there is any history of trauma to left side of chest.It can be muscular if he has prolonged abnormal posture while sleeping.Such pain would go away by taking anti inflammatory drugs like ibuprofen or naproxen Is there presence of any skin vesicles associated with redness and burning sensation over the skin? If yes,it can be a sign of herpes zoster infection. Is there complaints of low grade fever or fatigue or decreased appetite?This is to rule out pleural disease.In case if above complaints are present or presently mentioned symptoms get worsened,you need to take him to physician for further follow up. Also would like to know whether there is any associated medical conditions like hypertension,diabetes etc or is there history of smoking? If the pain is associated with referral to back or jaw,or sweating,breathlessness,you need to get ECG ,blood glucose,blood lipids done and blood pressure checked. Thanks and regards.