I'm just a little confused as to where, exactly, this bump is located. YOU say on the left side of your buttock and your HUSBAND says it's inside the buttock. If it's as YOU say, on the left of your buttock, it could be a number of things. If it's inside your buttock, is in fact, your anus, then I'm going with hemorrhoid(s) If the Prep H helped and you feel more pain while sitting or running, all three of those point towards hemorrhoids. Have you ever noticed a bit of blood on the toilet paper after a bowel movement? As long as it's a just a small amount, it's a fair guess it's a hemorrhoid. There is nothing unusual about it "suddenly" starting to hurt. Hemorrhoids do grow or you develope more and it can be years before they actually cause pain or bleeding. My first piece of advice is STOP poking it! No wonder the poor thing is irritated! Second piece of advice, see your doctor soon. There are things they can try to keep the swelling down or stool softners so your BMs won't irritate them so much. Surgery is most often reserved for those with really horrible cases and you don't sound anywhere near that point.
So, no poking, see your doctor.
Peace
Greenlydia