It really is hard to know where a safe place would be other than going subterranean.
What would the primary targets be in a nuclear war? military installations, fuel depots, energy generators.
If cities are targeted it would only be for maximum human kills and outside the initial impact zone
you would have to be below ground and as others say, would you really need to be alive?
The most likely target for a nuclear attack of very high magnitude, would be another country which also has nuclear capabilities, you know.
It would not make sense for a nuclear power to attack a country which does not have the capacity to retaliate after the first attack, keeping that in mind, I would be comfortable to affirm one would be very safe by keeling oneself away from countries in Europe, Russia, the United States, China, India and Israel. Those are the ones who claim to hold fission weapons.
If one lives in a country like Colombia, Bolivia, Pakistan or Thailand, where are are not nuclear programs, then there are very low chances one will be a primary target of a super power like the United States or Russia.
Though, in an scenario like a nuclear winter, then ones location would not be very relevant, as all locations ln the planet share the same atmosphere, but at least radiation would not be an immediate problem.
I still believe one is not supposed to think about nuclear apocalypse all the times, and try to live one's life as its fullest, instead.