Pain in the left facial bone may be caused by the following: 1. There may be trauma to the area. For example, a direct violent blow to the bone may cause a bone contusion or even a fracture, resulting in pain. 2. It may be caused by prolonged pressure. This condition is often seen when the patient sleeps in a prone position or in a long-term lateral position to the left side, which may cause pain due to long-term pressure on the left side of the skull. 3. It may be caused by cold. For example, if the patient is in a coma or drunk, the left side of the face is exposed to cold objects for a long time, which may cause aseptic inflammation and pain. 4, it may be caused by inflammation or infection, often due to the patient having infected lesions around, such as periodontal disease or toothache, which may also cause pain in the bones of the left side of the face. 5, it may also be caused by the patient chewing hard objects excessively for a long time. For example, if the patient has bad chewing habits, using the left side to chew for a long time, and the food eaten is hard, it will also cause pain on one side of the facial skull for a long time.