You can expect localized and downwind contamination from the explosion dispersing radioactive materials. If you are near enough to see or hear any local bomb blast, assume that it includes radiological or chemical agents.
You should move away from the blast area as quickly as possible. If the wind is blowing toward you from the direction of the blast, travel in a direction that is crosswise or perpendicular to the wind as you move away from the blast area. If possible cover your face with a dust mask or clothing to avoid inhaling potentially radioactive dust. Upon reaching a safe location, discard outer clothing, then shower as soon as possible.