This is a phrase based on the iconic Doofenshmirtz phrase, "Wow, if I had a nickel for the every time I was doomed by a puppet, I'd have two nickels. Which isn't a lot, but it's weird that it happened twice, right?" The phrase is not only a shortening of the phrase, but makes it easy to add to a conversation without jumpcutting to "haha funny reference".
Dude, this girl fell in love with me, dumped me, forgot she dated me, fell in love with me again, and dumped me AGAIN! Sigh, you know what they say about nickels and strange occurences...
It is said of the situation where a person has the bad luck to make contact with his testicles against an undefined surface or object, intentioned or not.
Given the nature of the word, it is more appropriate to design cases where the interaction is made with a moving object, for example, a ball.
Although it is extremely painful for the victim, it tends to be considerably funny to people who witness it.
Today in the baseball game the pitcher took a nutshot; the baseball hit him in the nuts.
Man, I just watched the funniest nutshot video ever.