I have gallstone measuring 15 mm in size and having stomachache after heavy meal i get a bloating feeling as well. what shall i do?

Consultation: Consult with your doctor, or a general surgeon. You're symptoms as presented are nonspecific, and really only a more complete history with a physical exam can yield the best diagnosis and plan. The only treatment for gallstones is removal of the gallbladder, usually done laparoscopically using four small incisions. The problem will be correlating the symptoms to the gallstones - no guarantees.