It's called tonsillolith (tonsillo=tonsils and lith=stones). They are small food particles that gets trapped in the folds of your tonsils. They stink. When they get big, its starts coming out. The only way you can remove it is to express it using your fingers or a long q-tip. Or if you can inhibit your gag reflex, use a water pik and channel the output to that particular fold. Make sure waterpik is set to the lowest setting because it can hurt you.