It's not technically tinnitus, but it can happen along with it. It's like an eye twitch, but it happens in your ear canal. You are hearing your inner ear/jaw muscles rapidly twitching, which causes your eardrum to vibrate. It's not serious and like you said it clears up by itself pretty fast, and if you try stretching your jaw, massaging the area, and relaxing those muscles it will clear up even faster. It's mildly annoying, but totally non-serious.