In fact, only America has ever actually used a nuclear bomb in a real war. On the balancing side, they've had a series of de-escalating disarmament treaties with the former USSR, so could be argued to be heading in the more peaceful direction than counties further down my list.
In the game Civilization I know that Gandhi will always, left to his own devices, eventually nuke me, because of a historical in-game joke. The real world is a lot less predictable.
http://www.thecrimson.com/article/1983/3/7/the-truth-about-g...
https://www.washingtonpost.com/news/worldviews/wp/2015/09/03...
There is a belief that any nuclear war will destroy the world, but that isn't true. A global war would be horrific, but civilization would survive. A war with 2-3k nuclear detonations is better than one with 20k.
Particularly, tactical nuclear weapons need to be destroyed. They are more likely to be used because they aren't a holocaust on a rocket like strategic weapons are.
Humanity will survive. Civilization will be utterly destroyed for a long time to come.
Also the humans that survived through Greenland had prepared for generations to live in hardship. Those left after any nuclear war certainly won't have been living their lives in nuclear winter world, no matter how good the doomsday peppers think they are.
But entire continents (S. America and Africa) would be entirely untouched by direct attacks.
The only risk of total collapse is deep and long nuclear winter. Even in that event (which I don't really think is realistic) coastal areas would fare better.
This is an excellent way to illustrate so many problems of this nature. "If X is a real concern, why hasn't it happened to us yet?" is such a huge problem in so many organisations, and it's so frustrating.
For the smaller players like North Korea or Iran, who are credibly threatening to use nuclear weapons in the next decade, but have no credible possibility of doing it at superpower scales, nothing much. They face annihilation if they launch, regardless. However, some of these smaller regimes are signaling that they are willing to face annihilation to get their strikes in. How much of this is game-theory-based posturing, and how much of it is true, well, that's for the reader to decide.
(Though I will toss in that at least North Korea is also signaling a belief that they will be annihilated if they don't get nukes, so given their belief system they may still not care, especially since it may be the case that North Korea === Kim Jong Un, and frankly, he may be rational to believe he's riding a tiger by the tail and must either get to and use nukes or personally face one sort of death or another. I see Iran as making more conventional power plays throughout the region, and even if their recent protests didn't topple the regime, it is likely that one way or another they are going to be forced to pour less resources into the nuke programs, either because they will need to placate the population, or because protest N+1 will topple the regime, or because they finally provoke external military or covert action that will result in regime change.)