If a meteor hits, you have bigger issues than nuclear fallout, like tsunamis, earthquakes, vaporization of water for an ocean strike that leads to weeks of rain, dust from a land strike cooling the planet, etc.
It's all a question of size. A 1Mt impact outside a city would probably not be that bad unless it hit a nuclear power plant or other nasty target. Probably a 1 in 1+ trillion risk but if all your asking is what's the worst that can happen it's on the list.