Should I Consult A Doctor As I Am Having A Red Spot On My Chest?

I am a 44 year old woman. I developed a dime sized red spot on my chest overnight. It is painful and burns a bit, and has a sort of "lump" under it. It is also hypersensitive. I've searched the internet and only find things that scare me. It doesn't look like ringworm, shingles, melanoma, and I haven't eaten anything different. I only take Estradiol 1mg. and started that about 2 weeks ago, but was on the estrogen once weekly patch since 2008. I weigh 105, and have always been pretty healthy, but did lose a grandmother to breast cancer. Do I need to have immediate concern about this, should I get blood work done, and should I see my ob-gyn or my regular doc.?