It can be a disease of the shoulder joint itself, such as inflammation or injury of the shoulder joint; But sometimes shoulder pain is not necessarily the shoulder itself. Neck diseases, such as the most common cervical spondylosis, can cause shoulder pain.
Guiding opinions:
If it is not the chest, it should be rhomboid muscle or rhomboid muscle injury or intercostal neuralgia. If it is deep, there should be other symptoms. There is no organ on the left except the lung, and the liver on the right is lower. If it is between the spine and the scapula, erector spinae's injury can also be seen. If it is deep pain below the scapula near the spine, you can consider the right gallbladder and the left heart or stomach. Visceral lesions will be combined with its main symptoms, which should be muscle strain.