North Korea has the bomb. This is a fact. The Kim Dynasty has been trying to build one for several decades as a means to solidify their reign in North Korea. North Korea using the bomb would definitely mean the end of the Kim Dynasty, which would be counter productive to why they developed in the first place. North Korea is isolated, with China (and Russia, I think) to the north and South Korea to the south.
The direction with North Korea needs to change drastically. They have the bomb, that cat is out of the bag. So the world needs to keep North Korea from selling it, to say Iran, which would mean Saudi Arabia gets it too, one way of the other. The other thing, which we likely are already working on, is developing methods to take the rockets out right after launch by disrupting their systems.
It is up to North Korea to make a move (which I would presume China would step in to block as any North Korean military effort endangers the Chinese border... turning it into a South Korean border). The US can not strike first.