Talk to Internal Medicine on Lump In Armpit

Hello I have small hard lump inside in my armpit with sometimes little pain to touch. I m 34 weeks pregnant with gestational diabetes . Today I go to gynecologist for checkup , she examined my underarm with her hand and she said that it Is nothing, it's a breast tissue and it's normal in pregnancy just leave it . It dissolve it's own .and I said give me any antibiotics but she said don't use any antibiotics or polyfex cream etc .So i still worried or not?? please help ?