Huh? I never really looked back there, but today it was really itchy, so I got up to look at it. There is this itchy, red, hair-covered bump on the back of my knee. There is somewhat dry skin around it, so maybe it was caused by that? Not really sure. It's kind of bothering me. It's a very prominent bump, though.
boil? could be the early stages of a boil - complete guess by the way. i really hope it isn't, otherwise prepare to enter a world of pain. back of the knee seems reasonable, it doesn't mean you're unhygienic per se, maybe just an infection on the inside (you mention hair, dirt can get into the hair follicles and such). best thing to do is grab some cotton, soak it under hot water and lightly dab the area, don't itch!
It's probably just an infected hair follicle. I was working in some dirty places for two days. I'll leave it alone, and I've just put some antibiotic ointment and water on it. And for the dry skin, some hydrating lotion.
