Does Black Scab With Reddish Ring Around It On Leg Indicate Spider Bite?

Hi, I have a spider bite I think on my left leg and it has recently turned into a black scab. I think ive had it for about a month now and before it just looked like a zit so i tried to pop it and pus came out. Then about 3 weeks later it was still there so i did it again and now it has turned into a black scab with a red-ish ring around it and its about the size of a quarter. Is it a spider bite? If so what kind?