What Is Causing The Pain And Discomfort In My Left Armpit?

I have a second degree burn on my right hand that has a large blister. It doesn't appear to be infected, but I am feeling some pain/discomfort in my left armpit. Could this be a sign of infection? I would think it would be my right lymph node that would become swollen, not my left. Do I possibly need antibiotics or should I wait a little bit to see how things develop? Thank you.