My son is 3 year old and he woke up with a very toxic smell of poop not a normal smell what can it be?

Is he well?: If your three year old is well, this probably represents a dietary misadventure. If the child has signs of illness: fever, lassitude, not eating, vomiting; then sheer medical attention.

Virus or diet: In a healthy child, a "gi bug" (infection in the intestine) or eating something unusual can make a child's poop change character -- color, odor, diarrhea, etc. Those things usually go away quickly and don't indicate a serious illness. If the change stays around for 3-5 days, talk to your doctor. It will help if you take a picture or bring in a sample of the poop you are concerned about.