Swollen lymph nodes in armpits??

Hello, I am 2 weeks postpartum with my second. I noticed some pea sized lumps in my armpit area 2 days after delivery, most of them gone within 3-4 days when my milk came in. But there is just one remaining which is bigger kind of hard and movable. With all the hormones and sleepless nights this thing freaks me out!! I can bearly sleep at night thinking this is something bad. My doc told me its is probably harmless but to wait few more weeks to see if it goes away by it’s own. Any of you have the same issue?? And did it go away? And I haven’t had anything like this with my first.