Oh, dear. Rawhide can be so dangerous. It shrinks when it is processed and can swell when swallowed and cause an obstruction. Gastric juices don't break it down. It is also processed with toxic chemicals.
If he can't keep food down and there is blood in his vomit, I think you need to take him to the emergency vet.
Rawhide - Danger in Disguise | CupOFdog | Dog Site for Dog People