Hello, my name is***** and I have over 20 years of experience as a veterinarian. I understand your concern about Coco given that he ate a large amount of Monterey Jack cheese last night and has a history of a previous episode of pancreatitis.
The short answer is that yes you do need to be concerned, but it is good news that he seems fine this morning.
Pancreatitis, an inflammation of the pancreas resulting in increased production and release of pancreatic enzymes causing abdominal pain and vomiting, can be triggered by several things and ingestion of high fat foods is one known trigger. Cheese is a high fat food.
So at this point a close watch is indicated.
It may also be very beneficial to feed a low irritant, low fat, high fiber diet for a few days to try and prevent trouble. You can purchase Hills i/d or Royal Canin Low Fat Gastrointestinal foods from your veterinarian or make a homemade diet to feed for a few days.
A homemade bland diet consists of 1/3 boiled, minced, white, skinless chicken or boiled, lean hamburger, all fats and juices drained off the meat, and 2/3 boiled, plain, white rice or mashed potatoes mixed with some low salt chicken or beef broth to increase fluid intake. Add 1-2 tablespoons of canned pumpkin (not pie filling, just pumpkin) to each meal for fiber.
If things go well and he doesn't vomit feed him the bland diet for 2 to 3 days then slowly start to mix back in his regular food, a little more at each meal. It should take about 5 to 7 days to slowly convert him back to his regular diet.
If he seems at all nauseous you can give either:
1) Pepcid ac (famotidine) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 12 hours
2) Prilosec (omeprazole) at a dose of ¼ of a 10mg tablet per 5 to 10 pounds of body weight every 24 hours
These are both acid reducers and either one should help him feel better. They are quite safe and can be used for several days if necessary.
If he vomits even with feeding the bland diet and giving one of the acid reducers, runs a fever (more than 103F rectally), has a tense painful belly or if he refuses to eat he should see a veterinarian for an examination, diagnostics, injectable anti-nausea drugs intravenous fluids and supportive care.
Best of luck with Coco, please let me know if you have any further questions.