In this community, we are not necessarily medical professionals, but ladies with experience of brreast cancer. Most of the time, a sudden lump in your armpit is duer to something other than cancer, but it could still be a sign of infection or other problem. Making the decision to get it checked out is good. Is there a women's clinic in your area or a reduced-cost regular clinic? You can check with other assistance organizations (food pantries, First Call for Help, others) who may be able to help you find a clinic. Also, try contacting the American Cancer Society in your area, as they may know of other resources. I am thinking of you.
Tumors usually arent tender but still go see a dr. They palpate it, do mammography and take fine needle aspiration and send it to pathologists in order to see if its cancer cells or not. There should be several ways to reduce the cost for a check up like cheerpul nicely described, use it.
Thank You both for your feedback. That is very helpful and great advice. I did call around today. I didn't feel like I got much help but will press on tomorrow. I got mixed messages about the severity of it, but for my own peace of mind I want to get it looked at. Thank you again for your help!