andrewyun1,
I've read and re-read your post several times trying to ascertain whether the stitches are "fresh" and still in place, or you have a scar from many years ago which required stitching, and the stitches presumably removed. (your use of the word stitches suggests that they might still be there).
If you refer to stitches presently in place, and the wound or incision not yet fully healed, it's highly inadvisable to fly, particularly if we're talking about an abdominal incision. After proper healing, and the stitches are removed, they present no impediment whatsoever to acquiring a professional pilot's licence.
Following on from that, if it is an old wound or surgical incision that was stitched, and they've been removed long ago, show off your battle scars and go flying.
Regards,
Old Smokey