Holding the oatmeal

Another way of saying that you need to throw up/vomit but can’t because there is no where for you or someone to let it out. (The oatmeal part coming from that fact that oatmeal looks like vomit)

Ex1. Oh no... I think I’m gonna have to hold the oatmeal.

Ex2. Jenny needs to leave, now. She’s been holding the oatmeal.