They might make her sick. They might not. It is quite amazing how dogs can eat food that is no longer fit for human consumption. Their digestive systems are not like ours. They can eat smelly carrion, and gnaw on old bones of deceased animals and be okay.
There is nothing literally "toxic for dogs" in the chicken nuggets (such as onions etc) -just meat which is past its eat-by date.
My advice would be to not panic but keep a close watch on your dog. If she/he is sick, then that's okay so long as the vomiting stops after once or twice and there are no other symptoms.
Usually when a dog has eaten something it shouldn't have, it will vomit to get rid of it, then pretty soon afterwards be ready to eat food, and there won't be any other symptoms such as tiredness, lethargy etc.
If you see ANYTHING which makes you concerned or which is unusual in his/her behaviour, or if your dog vomits more than twice, please do take her to a vet quickly.