Could also be an abdominal hernia, where you have a tear in your abdominal muscle wall and a part of your intestines are pushing through. That only gets worse and can be fatal if left to fester! Happened to a friend. He ignored it at first until the muscle wall ripped more and he got a football sized bulge sticking out. He almost died because it blocked his intestinal flow and he got septicemia (blood poisoning) that has now damaged his heart, liver and other organs. Put him on permanent disability at age 42.
Bottom line, don't ignore things like that, see a doctor right away.