It could be your gallbladder, something with your stomach, or even a lung issue. Go see a doctor if this doesn't get better in a few days, if you get worse at all, or if you get any new symptoms. When you go, be very specific about your symptoms. Any shortness of breath, coughing, or other lung issues? Is it worse after eating, especially a fatty meal? Do you have any nausea or vomiting? Any back or shoulder pain? Any pain or difficulty when using the bathroom?
Write down when your symptoms started, what (if anything) makes them better or worse, the severity, and anything that happened around the time this started. Take this list to the doctor's appointment. If you don't have any lung symptoms (other than pain when taking a deep breath), it's probably a digestive issue and you probably need to see a gastroenterologist. If you do have lung symptoms, it could be a lung infection and you could have inflammation in the lining of the lungs, called pleurisy.