I will say getting kicked in the parts hurts, a lot. You think a little tap hurts, and then you get kicked with all of someone's strength. But it doesn't hurt at first. Its more of a lingering pain, like something that is very hot feels cold at first and then turns hot. There are only few other pains in this world that can match a full-fledged kick to the nuts.
Like heartbreak, but then again, I want to keep this on physical pain. I would say that accidentally spilling or rubbing hot sauce on your one-eyed wonder worm hurts excruciatingly.