Hi, im a 21 yrs old female and I had my nipples pierced almost one year ago. It is very painful if your a girl and I also heard it can mess up the nerves and arteries in your breast. Later on in life if you ever want to have kids and breastfeed it might be very painful or not possible at all.
My nipple rings were always pushed against my bra and when moved were always hurting. They soon got better but every time I had sex they got infected again. I finally took them out about three months later. My breasts have healed, thank goodness, so I recommend you do not get them. They may look cool, but its just not worth all the trouble.