Basics!! This past year my group has explored needle play. When krissi visited my one-time college roommate in July, she made public that he was to be used as a urinal by making a “ladies room” badge (originally a printed copy inserted into one of those clear plastic nametag sleeves – the kind one gets at conventions) and pinning it to a nipple. These pins (and also safety pins) aren’t as sharp as needles and often produce a little short-lived (and manageable) bruising when they are forced through. If the nipple is really sore the next day the tag is shifted to the other one. Seldom have we skipped badging entirely.
And yes, we have attached badges to the genitals, both sacs and penises. They heal quickly.
We do not make insertions near the anus – too much risk of infection.
Then pain of pinning badges to their bodies is a normal and desired part of development. Just make extra double sure that the pin and the site of penetration is thoroughly disinfected beforehand,