You could have an inguinal hernia.
It's a weakened area in the wall of your abdomen.
In some people a piece of the small bowel can slip through the area and get trapped.
When that happens, generally speaking the opening loosens and the bowel goes back in place.
If that doesn't happen the little piece of bowel can be starved of blood flow and you have a serious situation on your hands (so to speak).
You need to see a doctor before that happens.
Inguinal hernia surgery is simple and safe and you don't have to worry about that opening ever again.
I advise you to make an appointment with your regular doctor and let him or her refer you to a general surgeon.