I am not a vet...but there is a decent chance that it is more than just an upset stomach.
First of all from all my experience with dogs and vets...table scraps
are no good for dogs...certainly this includes chicken marinated in a zesty sauce. Dogs get all they need from their dog food.
Blood in the stool is always potentially serious and if there is blood in the stool for more than one day....I'd bring the dog into a vet....
AND NEVER GIVE A DOG A CHICKEN BONE.