I had a similar hernia right above my belly button, called an umbilical hernia. I also had 2 inguinal, in my groin, on the left side. I had all 3 repaired in one operation. Have the doc look you over really close and make sure you don't have any more hernias because while you are down under anesthesia it is nice to get everything fixed in one trip.
If you do not get it fixed it will grow bigger over the years. I let my umbilical hernia grow and finally got it done when I suffered the inguinal hernias because those actually caused me pain. I think I waited about 15 years or more before I repaired it and it grew from the size of a pea to about the size of a grape.
What is causing the bulge is a tear in the muscle, happens there where the fibers attach to each other with connective tissue, and the peritoneal lining inside your body cavity is poking out. If you let a hernia get too big the peritoneum can get stuck poking out and that will cut off the blood supply and cause death of that tissue, bad thing. This is called a strangulated hernia. Along with that peritoneum can also come the intestine which can get strangulated.