What if a pet eats Terro ant killer. my 70 lb Boxer ate a small amount of it and he is not acting sick what should i do?

If he did eat a small amount, I doubt anything would happen. Don't worry, that stuff is for killing tiny ants, and you have yourself a big boxer. It most likely won't effect him. Apple seeds contain enough arsenic to kill a worm, yet it would take 20,000 seeds to even make a human sick.