While cooking two small prawns fell on the floor and the dog got to it. That was yesterday morning last night vomiting three time. What can I do. Are they poisonous

They're not poisonous, however dogs can develop allergies to sea food just like us.

Because he ate two shrimp and is having a reaction, I would assume he is either having an allergic reaction, or got a little bit of food poisoning.

As long as his mentation is good, just keep an eye on him and keep him hydrated. Give him a easy-to-digest meal for the next few days to help calm his stomach, such as browned hamburger and rice or boiled chicken and rice.

If he continues to vomit come Monday, I'd take him to the vet...

Thank you Lucky098, thank you for taking the time much appreciated

He may be allergic but they are not posionous.