Suggest Remedy For Skin Rash

Yesterday I took my jeans out of the dryer and put them on and wore them to work. During the day I thought I felt like a pimple or something on my left thigh and it kind of itched but I ignored it. When I got home last night and took off my jeans, I had about a quarter sized red circle with brusing around the outside. It wasnt a pimple or anything and now this morning it is about the size of a half dollar and more brusing. I havent ran into anything and I am not sure what this could be. I tend to sometimes get lumps on my inner thigh that eventually you can pop and puss comes out and then they bleed and it heals but this is something new as its on my outer thigh.