hello, there are two possibilities in you, first does this pain increases on deep breathing, is it Sharp or associated with cough, if yes it is likely due infection of lining of lungs. This is most likely due to viral infection and will resolve in few days. If doesn t then it needs evaluation. You should have otc medicine like paracetamol or ibuprofen or diclofenac for this kind of pain. Secondly, it may be due acidity and gastritis. Do you upper abdominal pain, nausea, bloating, burping, increase in pain on food, sour water feeling in throat or chest burning, if yes it further supports the diagnosis. You should avoid fatty, oily and high calorie diet. Have some walk after having food instead of taking rest. Have multiple small meals instead of heavy meals. Have regular sleep habits and avoid stress. Lots of green leafy vegetables, fruits. Avoid smoking and alcohol if any. You can get prescribed tab Pantoprazole 40 mg beforebreakfast once a day for 2 weeks.