You probably broke a capillary or nicked your throat. I've had the same thing happen to me.
That has happened to me once before - it was because i had cut the back of my throat with my fingernails by accident. I don't know, maybe that's what happened to you. My doctor at the ed clinic always asked me if that was happening, so if you see one i would tell them so that you can find out why/if it is a big issue.
Hope that helps x