it could be a cyst but there are other possibilities. you would need to see your medical provider so you can have this lump properly examined and diagnosed.
i am a male who has a hard lump behind my nipple that only hurts when it is touched and wondering what it could be? . i used to have my nipples periced 6 years ago but only had them in for a year and now behind my left nipple there is a lump that only hurts when it is touched or pressed on.