My son has the same problem before and I got the same advice from doctor like that described by IRON - that works for my son.
That also depends on how tight the skin is. My son's jj skin will bulge up a bit (50%) when he start to pee, so his case is minor. Check that out on your son: if it bulge up a lot that looks like a ball, that's sort of serious and may need the surgery.
Better get the doctor to evaluate your son's case then decide.