nipples seem large in relation to the rest of your chest area, so my guess is that underneath is tissue there that could be excised. but only a doc could say for sure.
just curious, tho - do you feel any hard, fibrous tissue/lumps under the nipple at all? alternatively, you may just feel squishy fat, which is not to say that breast tissue isn't intermixed with the fat - that could be the case. however, one doc i saw mentioned that large nipples could be the result of a prominent case of gynecomastia during puberty, which could have diminished post puberty (and after all the crazy hormonal changes). even if there is no breast tissue, the gynecomastia during puberty could have left the nipples stretched