Mar 17, · Sternum or Breast Bone The organs in the thoracic cavity comprise of many critical organs of human body including the heart and lungs. This is the secondReviews: 6. Pain under the breastbone or pain in the chest bone can be caused by multiple causes like esophagitis, acute pancreatitis, muscle strain or indigestion therefore the treatment for sternum pain should be carefully addressed to the cause which is producing it. There are many organs under your right breast, such as gallbladder, right kidney, muscles, part of the lung and liver. The common causes of pain under right breast include hormonal changes, heartburn, trapped gas, and stress.