Looks like when my snakes have regurged worm before. Maybe there was something nasty in the worms that needed to come out? If you still have the container that he was fed out of last, give it a sniff. I've opened mine up and smelled what was definitely e.coli in them before. He looks pretty bloated in that pic. Was he just puffing up because he was annoyed? If not, give him a soak and see if that helps.

Hopefully it was just bad worms or something disagreed with him. I don't know what you'd do if it was something more serious. But give it a couple days and see if he seems any better.