Re: What could this be?
First, since you're very worried about it being cancer already, I'd go check it out with the doctor or call some kind of help-line at your hospital and just talk about it with a nurse on the phone.
I get these every few months too. I used to have really bad acne, and I know any dermatologist would slap my hand for it, but I can't help but pop them. The ones "down there" usually turn out to be something like a blood blister. How they happen, I have no idea, and I do plan on asking my own doctor next time I'm there.
I read on a thread here earlier about someone with the same question. One response was that acne can come up anywhere on your body and if it feels, looks, and acts like a pimple, its probably just a pimple.