Large Red Rash On Inner Thigh With Pimple In Middle. Should I Be Concerned?

I have a large red rash on my inner thigh. it is warm to the touch and tender located towards the center. I drew a ring around it last night to see if it great and it has grown immensely almost to the size of my palm, could be larger. It is not itchy but when it first started It looked like a spider bite and had a small pimple looking thing in the middle. I washed it off and the pimple went away but I can tell that there is still a middle spot where it is most tender. Should I go to an urgent care or is there a over the counter anitinflammatory I should take..