Need a bit more info, but you do have options
So it's a bit unclear whether you have already had nipple reconstruction and it went flat, or are researching to find out how to prevent flattening after nipple reconstruction.
This is a problem that has dogged us plastic surgeons for quite some time. Although we can often get a nipple quite upright, the scarring and tissue remodeling combined with pressure can often lead to nipple flattening.
Either way, whether you have already had a nipple...