Sounds like a hernia
Hernias are holes in the abdominal wall thru which the inner lining of the abdominal cavity stretches out, creating a sac.
Common locations include the groin, the navel, and the upper middle abdomen. Hernias tend to protrude with any activity that increases abdominal pressure including straining, coughing, lifting, etc. I suggest you see a primary care doctor for evaluation.