To reduce stomach upset you can give Ranitidine at a dose of 1mg per kilogram of body weight or 1/2 of the 75mg tablet size every 8 hours for the next few days. You can take a wait and see approach and only give if he seems to have stomach upset, or you can give it for 24 hours and see how he comes along.
Offer small amounts of water often. He is likely going to be thirsty, but if he drinks too much too fast that can make him vomit.
Feed a bland diet of 1/3 boiled, lean hamburger (or boiled, white skinless chicken), all fats and juices drained off, mixed with 2/3 boiled, plain white rice. Feed several small meals a day. You might wish to add 2 tablespoon of canned pumpkin (not pie filling, just plain cooked pumpkin) or cooked squash to each meal as fiber will help push the wrapper through and cushion the intestinal tract.
If he is refusing to eat, vomiting seems very lethargic, has profuse diarrhea or has muscle tremors or seizures then an emergency clinic visit is best.
Please let me know if you have any further questions.