The main thing to watch for is if it gets hard, hot or the kitty gets a fever. Sometimes a little bit of intestine can fall through the hole and get twisted off, and it gets gangrenous and is a serious problem. Talk to your vet about whether what your kitty has is of this magnitude or no big deal.
Have the vet look at it. Sometimes they can be pushed back in, but will pop back out again. When one of my kittens had one, the vet took care of it by putting a stitch in the muscle to close the hole back up, when she was spayed.
its close to the navel. Is there any way to get rid of it?
Where? If it's at the navel, it might be an umbilical hernia.