[Ellie May]

I wouldn't rush to the vet or just let it go.
As Marci asked, are his gums pink?
How much does he weigh?
Did he get any foods yesterday that he doesn't normally eat?

Unless he ate a large amount of sand, I would wonder about what germs were present and if he found something else to eat...

Depending on his age, gum color and ability to hold fluids down, you may be able to wait awhile. If he has thrown up more than 2-3 times, it is best to go ahead with the vet or if he can't hold liquid down, etc.