Alright how the hell did I get a huge boil pimple thing on my thigh? It just appeared out of nowhere.

I woke up a few days ago and there it was on my thigh. The area around it was super red and puffy and my leg felt stiff as a board whenever I squatted down or bent just right. The stiffness has gone away and the puffiness has calmed down but it's still red and kind of puffy around this boil looking thing. It looks like a big white head pimple it was leaking earlier but I slapped a bandaid over it.