i hate piercings, and i have a very high pain tolerance.  piercings hurt like a sharp pinch initially, then a bit irritating when the jewelry goes through, and then it'll potentially be sore for the rest of the day and be sensitive to the touch for a few days.  on another note, i don't agree with piercings under 18 even accompanied by an adult, call me stupid or a bitch, but it's the case. generally can have a lot to do with your body still growing, but i know nothing of navel piercings. only know that a lot of shops here aren't keen on doing it.