Hi. I am no doctor, but I am glad you went to the dr. It is PROBABLY absolutly nothing. But my mom had that same symptom a YEAR ago...and we wish to god she had gone to the dr right after she noticed it.
She had THREE mamograms within that time frame, and the nipple would invert..then come back out for a while..then invert...and throughtout the whole thing the mamograms showed normal. I am NOT meaning to scare you...like I said chances are much more likely that its nothing, but please pursue it--even past the mamogram if it continues---my moms three mamograms never showed ANYTHING...now shes dealing with cancer shes had over a year. She has it in the nipple.
Good luck to you.
An inverted nipple can be a normal variation. However, if it appeared after maturity or if there is inversion of a previously non-inverted nipple, that should raise a suspicion of an underlying inflammation or neoplastic process.
I agree with a consult with your doctor. The antibiotic (Cephalexin) given to you would eliminate the possible infection as the cause of the nipple inversion.