Painless lump under armpit...?

I have a lump under my armpit, I noticed it a while ago when I was shaving under my arms, it is about the size of a pea and there is no pain to it at all. 
I am seeing my midwife tomorrow so I will mention it to her.
I am just wondering if anyone on here has experienced anything like this and if it possibly related to pregnancy, I am 35 weeks pregnant.