I was innocently cutting and chopping an Onion & the knife sliced half of my nail I obviously couldn't remove the sliced part of the nail as the pain would be excruciating and the skin underneath would be exposed.
I can't remember what I was eating, but I was having my dinner once and my jaw just clicked and locked out in place. From then onward, I've been able to pop my jaw - makes a rather satisfying sound to be honest.