What Is The Red Pimple On My Breast?

I had a red pimple on my breast that suddenly turned black. It is tiny (less than 1/8th inch). It is a little tender. There are spidery red vein marks radiating from it. I put Neosporin on it and the blackness receded to the size of a pinprick. Is it safe to assume that if Neosporin makes it fade, it's not melanoma? If so, what is it? Thanks for the help, I have no insurance right now.