Is pizza ok to eat if you previously had an upset stomach yesterday?

I'd wait another day: The problem with recovery is you often have cravings for stuff your system may not be ready for. Any fatty food, cheese, salsa, fried food, require increased digestive work & may trigger renewed sx. Steamed rice, noodles, macaroni without sauces, spaghetti, simple breads are all well tolerated during recovery from a GI disturbance.