Hi! I Was Shaving Yesterday And Noticed A Round Scab

Hi! I was shaving yesterday and noticed a round scab on my thigh. I was able to squeeze out some blood thinking it was an ingrown hair. Today the area the size of a silver dollar is swollen around the scab and there is a raised bruised bullseye. I also have had severe explosive diahrea. No fever that I can tell. My body does ache and I'm lethargic but I am obese and have fibromyalgia so it can be those. Could this be a spider bite and should I get in to the emergency room? Thank you!