You can consider surgical nipple and areola reduction. The procedure can be performed to reduce the size of your nipples to make them less prominent, and to reduce your areolae so they are better covered up by your bras.
Unfortunately only surgery can reduce the size of your nipple.
Fortunately, nipple reduction is a relatively simple procedure that can be performed using a local anesthetic as an office procedure.
Generally, you want to wait till you stop breast-feeding before undergoing nipple reduction surgery since there is a distinct chance of damaging the delicate milk ducts that leads from the deep aspects of the breast to the nipple itself.
Of course, there is a simple nipple reduction which...