Big deal...
Nothing's changed. I just looked outside and the sun actually came up this morning. The end isn't near and the civilized nations aren't going to do anything about the NK nuclear test except thump their chests and maybe rattle a few sabers.
Nor should they. North Korea may be run by a demonic fool but it is still a sovereign nation. Neither the US nor any other nation has any right to tell it what to do. If we don't like its actions then we can ignore it, stop doing business with it etc - which seems likely.
On the other hand, there's always the doctrine of might makes right so I suppose we could pre-empt any use of nukes by the NK's by using our own weapons against them - a few hundred well placed Tomahawk missiles, some bunker busters and well - hell - maybe even a nuke or two ought to take care of the problem.
Lost of options on the table - unfortunately no one has the cajones to do what's really needed and that's take out Kim Jong Il, dismantle the NK regime and reintegrate it with the more civilized South Korea. That's never gonna happen though so we best just learn to deal with a nuclear armed North Korea.