What nuclear weapons would this be? North Korea has made a nuclear test in controlled conditions. Yet they don't have a credible means of deploying a nuclear bomb, let alone the technology to make a warhead. If you were talking 5-10 years down the line (with no sanctions to stop bomb-making equipment getting in) you might be right. Today that wouldn't be a threat.
You don't need to deliver it very far when it's to be used on your own soil. In fact it doesn't have to be 'delivered' at all, just placed in a location that foreign troops will have to pass through or occupy (like a city) and then detonated. Pretty sickening, but the North Koreans have been capable of similar atrocities against their own people.
French Atomic Energy Commission says the NK bombed failed at getting a full nuclear detonation
If this is true then the only thing that the NK's have accomplished is destroy their own bargaining position, unite its previously semi-divided enemies, and strip itself of friends. I wonder what the hell they were thinking?