First off, don't worry. Your snake did not break it's jaw. Their jaws are made to dislocate both at the hinge and in the middle of the chin. This enables them to swallow items larger than their heads.
Secondly, it may have been that the pinky was too big, but I think a more likely reason was that your snake got spooked. My king snake did this once. He was nearly finished swallowing his mouse when something startled him and he spit it back up. This is an instinctive fight or flight response for them. They can't flee or fight with a mouth full of mouse.
I would wait a few days longer than normal to feed him, and feed him a slightly smaller mouse, but since the mouse never made it to the stomach, I wouldn't call it a regurge. Next time you feed him, give him lots of privacy. Put him in a small container, cover it or turn the lights out, and leave the room. If necessary, put the feeding container back into his viv and leave it there all night.