The US is now acknowledging that North Korea did indeed test a nuclear device last week. But given that the blast had a yield of under 1 kt, either the test was a failure or North Korea's nuclear program is far less advanced than has been assumed. It's most likely the former: developing a successful nuclear program is much more difficult than movies, TVs, and many analysts make it seem. This doesn't mean that North Korea isn't a threat...rather, it means that the time line is not as advanced as a successful test would have meant. If North Korea can't successfully detonate a device in ideal testing conditions, it certainly can't yet be considered a threat to deploy nuclear weapons. Furthermore, North Korea still doesn't have a demonstrable delivery capability.
All of this means that there is still time to try to encourage North Korea to back away from the precipice. Unfortunately but not surprisingly, it doesn' t look like the UN is going to be able to have much effect. The US must use all of its political and economic incentives (and sanctions) to force China and South Korea to isolate North Korea. Only if those states see that their aiding and abetting of the North Korean gulag state risks their domestic economic health as well as their relations with the larger international community will they take any serious actions against North Korea. The US, and only the US, can make this happen.