i don't know. i didn't see it; you did. there are many possibilities but consider a tonsillith (a tonsil stone that has dislodged). you can find information about cryptic tonsils and tonsillitis on webmd ent board or by a webmd or google search.
i get hard small pieces of what i think is gunk that has hardened that come out of my mouth. what is it? . sinus allergies sore throat