North Korea probably now has nuclear missiles. This is unfortunate, but dictator Kim decided to do this, there was no way to stop him.

The issue for the US, and for South Korea and Japan, is what significance to assign to this. I think that it does not need to lead to war. Kim thinks of North Korea as his property, and he does not want to get it nuked, so why would he launch nukes?

He may feel so much safer, with his nukes, that he would look for peaceful relations with other countries.

North Korea is a totalitarian hell. But we cannot change that by threatening war. Meanwhile, China is developing into a totalitarian hell; Xinjiang is worse than North Korea, if what I have read is anything to go by. And we cannot change that either. Since North Korea does not threaten to take over the world, we may as well make peace with it.