It is not unusual to have the nipples inverted to some degree, but if it is severe retraction then I suggest that the patient should have an ultra sound scan done and any pathology in the breast (rudimentary in the male) or have a mammogram done. Also if there is any lump then that should be biopsied with fine needle aspiration (FNAC). Assuming that all the results are favourable then it a minor surgery to lift the nipple and areola and elevate the same and stitch in such a way that the nipple will protrude and look more normal shaped. Any surgeon with experience of breast surgery in the women or a plastic surgeon should be able to do the same without any difficulty.