Pain in the bone under the left breast is considered to be caused by the following conditions: i. It may be caused by trauma to the rib cage, such as pain caused by local tissue damage from impact of hard objects, carrying heavy objects, strenuous exercise or contusions, etc. Second, it may be inflammation of the soft ribs, which may result in local pressure pain or skin redness and swelling, and increased skin temperature. Intercostal neuralgia may be a wandering pain, with the main sensations of pain being pulling pain, cutting pain or pins and needles pain. The pain may be caused by breast diseases, such as mastopathy and mastitis, which may cause pain around the breast. Considering that a variety of conditions can cause such pain, you can go to the relevant departments of the hospital for further examination to distinguish the cause and then carry out targeted treatment.