Can anyone give me any advice on what This could be?

Hey ladies, I have a nephew who is 2 years old. Last night he kind of chocked while sleeping but he was throwing up. This morning he has threw up 2 times, and it's clear like spit and a little mucus. He has a little diarrhea. No fever at all. He is up and active and happy, but then the throw up comes out of nowhere and has him gagging. What could this be? & what should I do for him?