Ok, I was hoping he just vomited once or twice and he was keeping water down.
This is sounding more serious so he does need immediate care.
Until you can get him to a vet, you can try giving him pepto bismal. 1/4 teaspoon, per 5 pounds of weight, every 6 hours.
You can also give him children's pedialyte drink, with a syringe or eye
dropper, to help prevent dehydration.
Rub honey, or pancake syrup, on his gums every 2 hours until he is eating normally again.
He could have the parvo
virus. It takes at least 3 vaccines, given 3-4 weeks apart, until they are fully protected. The parvo virus usually causes diarrhea too but it can start with vomiting.
He could have ingested a non-food object and now it is causing a gastrointestinal blockage.
He could have a bacterial or parasitic infection.
I hope this helps.
If you have other questions, please click "reply."