My son got a tiny mole on his back at around 7 months. As the years went on it grew. When he was about 8, it was the size of a pencil eraser. The doctor said it should come off, so we had it removed by a plastic surgeon. They thought it could possibly turn cancerous and I wasn't about to take that chance.
He is now 27. Now dermatologists would probably be able to removed it. We were worried about scarring, but remember this your son will grow and that means the skin will grow and stretch, also. So I really don't believe you'd have to have a plastic surgeon involved, except if it's in a place that would be noticeable, because my son did have a scar for a long time. Also, you know how kids are, if they seem something on someone, they will make fun of them and that's not good either. Kids can be so brutal. So I'd get the thing off regardless of what the doctor says. But that's just me.