I don't doubt that North Korea would fire a nuke at the South or Japan if they had the capacity. But I don't think we would use nukes unless we had the full support of both Russia and China in doing so.
Too easy to accidentally start a large nuclear war between parties who do have the capacity.
NK throwing a nuke would be China and Russia nuking us (South Korea) without our detecting so.
This is a game language. NK is their colonynor sattelite.