Ideally you should wait until your nipples are fully healed before doing any type of nipple play. It is important to wait through the entirety of the healing process because until 9-12 months your body has not finished developing fistulas. This means that you have a higher risk for ripping or tearing the piercing.
Also question is, does getting your nipples pierced affect anything?
Potential risks include infections (or even breast abscess formation), nerve damage, bleeding, hematoma (a blood-filled cyst), allergic reactions, nipple cysts, and keloid scarring (raised, red scarring). Unfortunately, nipple piercing is also associated with hepatitis B and hepatitis C infection, and even HIV.