If you take him to your nearest children’s hospital, they’ll give him some anti nausea medicine. Then within a couple hours they’ll give him a pedialite (sorry if I spelled that wrong) and see if he will hold it down.
We went through this with my son when he was like 8 months old, it was terrifying but he was ok. Kids get stomach bugs because they put so many germs in their mouth.
Good luck and I hope he feels better!