Food grade means it can be safely consumed.

Non toxic means you don't have to call poison control, but it isn't necessarily recommended for safe consumption. 99,999 times out of 100,000 your kid will be fine, but depending on what surfaces that play-doh sat on it could be contaminated with a pathogen that might cause an upset stomach/vomiting/diarrhea. So like any other day of your kid putting random stuff in his mouth, basically.