Nipple piercing is not only for the look of the piercing but also for personal stimulation, once healed nipple piercings can be quite erotic and will add sensation when the right jewellery is in the piercings.
You can get it done again once you're sure the piercing is healed inside as well as out.
No you are pretty much stuck with it unless you want to see a plastic surgeon $$$$.
When it's not healed, clean it with antibacterial soap of a liquid specifically for cleaning piercings.
That you decided to get a nipple piercing.
You can change it as soon as it's completely healed; female 6-9 months, male 3-6 months
If you wanna retire it, yes. Its best to retire it early :) If you mean to change it or something, no. Wait until its healed.
If the 12 year old has had the piercing for over a year, chances are good it's healed. If it was done by a piercing gun, then it could still be healing.
Until a woman is 18, it is illegal for a shop to do a nipple piercing on her. For men it's not illegal as far as I know, but most piercing studios will not pierce someone under 16, others may refuse to do nipple piercings on a male under 18.
Yes I have had lots of clients who have received nipple piercings and have successfully breast fed there children. As long as the piercings were done correctly and healed without issue breast feeding with the jewellery in or out is not and issue.
6~8 weeks for a light heal, no piercing is considered actually healed till it's at least a year old. But by about 6~8 is good for what we call a light heal.
An inverted or occluded nipple piercing needs to be done by an experienced professional body piercer who knows how to properly do an inverted nipple piercing. The technique is some what different from a standard nipple piercing, skill and knowledge needs to be used in order to correct the inversion. I have done many of these "repair" piercings with the end result being a proper outward displaying nipple. The inversion is partly due to the beast connective tissue and how the ducts and nipple connective tissue seems to be too short thus causing the nipple to be inverted. So find your self a body piercer who has at least 5 years of better of actual piercing experience or be prepared to travel to have it done correctly. Knowledge of human anatomy is a must to complete this piercing properly, but trust me once it's done right and healed you will be very pleased.