Suggest Treatment For Sore Red Spot On The Thighs

I have a sore red spot on my inner thigh between the knee and groin. There is no sign of a spider bite. The spot is 1"X 2" and about 1/2'-1" deep. It will not move around like a fatty tissue(cyst). My leg has been sore for several days but I have only noticed the redness and lump today. i thought I had a pending bruise but now am worried about a spider bite or cancer. I viewed many spider bites on the internet but am not satisfied it's a bite because I can't see a bite mark. I have PCOS but but have never had a cyst on the exterior of my body related to this.