Actually I do not believe the N Koreans really do have a workable bomb. There has been no test of one despite disturbing events which imply that they do.
Well, I’d put it this way:
They DO have a workable bomb, and have successfully tested nuclear devices several times.
They do NOT have a workable long-range delivery system, as their ballistic missile tests have demonstrated.
I don’t doubt that what you intended to say was that they don’t have a workable nuclear-equipped ballistic missile.
What is frightening about Iran is that they are well ahead of North Korea on ballistic missile devices, and also would have a significantly easier time purchasing such technology than isolated North Korea.
I wonder what will happen when Kim Jong Il gets close to death. But I believe that Iran is the much greater threat.