Thank-you for the information. A problem like this can occur with a little dietary indiscretion, which in the case may have been the grass. I would withhold any food for the next 24 hours. you can offer water so he does not dehydrate. This is the gold standard for vomiting.To settle his stomach there are several medications that can be used that are over the counter and should make Nero's stomach feel better.
Famotidine (Pepcid A/C) LINK HERE (The typical dose administered is 0.25 to 0.5 mg per pound (0.5 to 1.0 mg/kg) every 12 to 24 hours.)
Prilosec OTC (Omeprazole) LINK HERE (The typical dose administered to animals is 0.25 to 0.5 mg per pound (0.5 to 1.0 mg/kg),
Rantididine (Zantac) every 24 hours or once daily.)- LINK HERE (The typical dose administered to animals is 0.25 to 1 mg per pound (0.5 to 2 mg/kg)every 8 to 12 hours.)
Any one of these medications should help with nausea. If he starts vomiting again or starts with Diarrhea, than at that point I would have him into the Vet. Usually something like this will resolve itself within 12-24 hours is it is dietary indiscretion. If he gets more lethargic, does not want to eat tomorrow, or anything else comes up over night, then I would have him see the Vet in the am or sooner to the ER Vet depending on how bad it gets. I am hoping that he will feel better by morning.
You may want to speak with your Vet about Science Diet Z/D or Purina H/A for an allergic diet while trying to determine what he is allergic to. I usually suggest Natural BaXXXXX XXXXXD which has a unique protein source like Bison which works well with food allergy dogs. Please let me know if you need further help and I will be happy to continue with you. Joan