I have a very small pimple looking thing on outer labia on left side. It just popped up yesterday, I applied heat to it, and it isn t as sore today. It s not hard, and is the same color as the surrounding skin, and had a head on it like a pimple on your face. This evening, it popped and pus and blood came out of it, same as it would with a pimple on your face. This happened only one time before, and it completely went away on it s own in maybe a 3 day period of time. What causes this to happen? Is there anyway to prevent them? Are these things common?