see a good breast expert, someone familiar with the lactating breast.
Sounds like it may be an inflammed or cystic type lesion of the montgomery
gland BUT you need to know for sure.  And take the time and effort to find
a dr who is really knowlegeable,  even   if she has to  pay for the consult
out-of-pocket.  I'm sure we can all share horror tales of stupid surgeons
removing plugged ducts etc and of course damaging the course of lactation
for the mom.  I know a couple in the Phila Pa area.Sincerely, Pat in SNJ