Hundreds of nukes have been set off above ground since 1945. There was no nuclear winter. I suspect a nuclear war won't be the cataclysmic event feared. Of course millions will die and perhaps billions but not all 8 billion of us.
Actually it is thousands, There have been 2055-2060 nukes set off over a timeline of several decades Like over 6 plus decades, But again that's over a decades. Any one want to track cancer rates since 1900?
The world’s nuclear powers have more than 12,000 nuclear warheads. The U.S. and Russia have over 5,000 nuclear weapons each. I would also point out nations do tend to "Salt" their bombs.
Only 2 nuclear devices have ever been dropped on inhabited areas, We saw what that did.
Imagine 3000 nukes (Far more powerful than Gadget, little boy, and fat man) used on cities and inhabited areas all at once. Add in radiation fallout that is going to hit all at once and a complete loss of infrastructure and your looking at a Toba catastrophe level event that if it doesn't wipe out all of humanity it will surely destroy civilization as we know it, and may well cause another genetic bottle neck.
Look at what a little cold did to the world in 2020.
The people that don't die in the blast are going to die due to radiation sickness and the rest of poor talking monkeys are going to starve to death or eat each other.
I know one thing for sure it's not going to be as fun as a bethesda game.