If you have ruled out a hormonal cause, such as elevated prolactin, it is not unusual to continue to produce a nipple discharge from the holes left from the piercing. If these holes do not close, the discharge may last months or years, especially if you continuously check to see if it has stopped (so don’t touch or play with them).
On a similar note, tongue piercing has serious long term effects; it can cause gum damage and crack the enamel on teeth especially after months or years of wearing the stud. So unless you like the idea of adding additional metal to your mouth from cavities or gumming your food before your time, take out the stud. 🙂