First of all, Israel does not have the capability. It could only set back Iran's progress, not stop it. Secondly, there being a chance of something is not an argument. There is a chance Pakistan could use its weapons against Israel as well. Where was the Israeli attack then? There is a chance North Korea could use it against the United States. And so on. None of this justifies military action.
If Iran gets the bomb then it becomes the most likely country to have a bomb and use it. I'd rate the chance of Iran using an atomic bomb within a decade after it has a bomb and the means to deliver it as being in the 1 to 5% range. Still not very likely, but enough to trigger the doctrine of preemptive war to prevent it.
Whereas, the only chance North Korea will use its bomb is if South Korea invades the North, and that ain't gonna happen. North Korea is a vile regime, and its leadership should be sent to the gallows for their crimes, but their reasons for developing a bomb are those of national pride and self-preservation of their regime. To a large degree that is motivating Iran as well, but Iran has other reasons as well, reasons that could lead Iran to use the bomb as something other than as a threat of mutual assured destruction.
