Hello, Does he have any history of injury to shoulder? History of heavy weight lifting? Get an x Ray and consult orthopedic doctor .It could be fracture of bone or ligament tear. Gastritis - try eating small meals instead of three large ones whenever you can.  Avoid foods that irritate your stomach, especially those that are spicy, acidic, fried or fatty.He can take antacids if gastritis is severe. He should manage stress .