While that rat certainly put a noticeable lump in your snake, it's going to be fine. I would avoid handling or disturbing him for a couple of days while he digests this larger than normal meal. Also make sure his warm side temp is in the proper range, since it will help with digestion.
For future reference, many keepers don't feed anything larger than a small rat, even to their adult Ball Pythons. Looks he has taken a liking to rats. I don't think I'd mess with mice anymore![]()