This nuke map considers what would happen if Iran exploded a 20 kiloton nuclear bomb on a ship beside the U.N. Headquarters in New York City. The blast radius affects Manhattan, Brooklyn, and Queens.
And here’s the same point of attack with a 45 kiloton nuclear bomb.
The largest Pakistani nuclear bomb tested is thought to be 45 kilotons. It is not unthinkable that an Iranian nuke could be in the range of 20 kt (Nagasaki bomb) to 45 kt (Pakistani test bomb). The image below is from the 20 kt nuke map.