There are many reasons that can cause pain underneath the collarbone, which may be tissue damage of the local muscles underneath the collarbone, chest disease, or lung disease. 1. Local muscle tissue damage: tissue damage is caused by trauma to the muscles below the clavicle or overloaded exercise, making the patient feel obvious pain when pressing the clavicle. After sufficient rest, the pain can be relieved and the tissue function can be restored. 2. Pleural disease: If the patient has pleurisy, its inflammatory reaction can induce localized pain. Generally speaking, the range of pain is relatively large, in addition to the pain of pressing below the clavicle, there may be multiple points of pressure pain. 3. Lung disease: if the patient has lung disease such as tumor, the tumor may spread to the ribs below the clavicle, which affects the local nerves, and the pain will also be felt by pressing, and the pain is strong and sharp. In addition to the above reasons, there may also be costochondritis and lymphatic system diseases, so patients with symptoms of pain under the clavicle, must go to the hospital in time to check, according to their own condition and follow the doctor’s instructions for treatment.