Every weapon ever invented, has been used in war. Nukes will be used sooner or later. America and Russia have thousands. The rest of the world has only hundreds, all told.
Fortunately, Russia is run by merely a thug, and not a Hitler style mad-man. England, France, and Israel are friends. Pakistan and India have theirs aimed at each other. Iran will have them in quantity real soon, to aim at Israel.
China has enough to hurt, but not devastate America. It is very doubtful though that they would volunteer for becoming incinerated, for N. Korea's sake.
Shall we wait until N. Korea has hundreds, giving them the capability of incinerating half of America?
Actually, it would be a strong bet that all Trump has to do is announce that America has changed it's policy from "No-First-Use-Of-Nukes" to "Use-Nukes-As-Needed". Then declare a technical state of war against N. Korea. Then we could "legally" make a "first-Strike" against them, if the little chubby one fails to get the message.