I think Putin doesn't *want* nuclear war, but he wants to be feared and respected and isn't afraid to use nuclear war as a way to achieve those. I definitely think that the possibility of nuclear war with Russia is far greater than it's been for decades. I'm incredibly concerned with some of the actions Russia has been taking recently and Putin's instability and megalomania is very concerning, especially in light of no trustworthy leadership in the White House once President Obama leaves office. Trump would nuke Florida if he threw a temper tantrum, much less a foreign country. Clinton, well, who knows how she would respond in a nuclear crisis. At least she and Putin both love money - maybe they could bond over that.
I do think North Korea and Iran, and of course terrorist organizations, are concerns, but unlike Putin I don't think they'd be able to do more than nuke once city before we bombed them out of existence. Russia could definitely do serious damage just due to the sheer size of their arsenal.