When it comes to nuclear war, there are a lot of tales out there that would seem to tell you that the world would come to an end. Of course, that's not necessarily true, at least, depending on the size of the nuclear war.
When a nuclear bomb detonates, there are different danger zones depending on how far away from the blast you are. These zones are separated by different kilometer ranges. The first zone can leave anyone in range with third-degree burns from the sheer heat that comes from the radioactive blast. The second zone can leave second-degree burns, while the last zone can leave first-degree burns.
These blasts also pack a pretty detrimental wallop, which can topple buildings and send blasts of air traveling at over 750 miles per hour. That same blast also vaporizes the materials in the ground where it detonates, which leaves a crater. The vaporized material gets sent into the skies in the form of a mushroom cloud, which creates radioactive fallout.
It is possible to survive nuclear blasts, assuming you're far enough away from it, inside of a building made of radioactive-resistant material like metal or cement (that hasn't collapsed from the blow), and you would need to keep away from the radioactive fallout coming from the skies, which would remain toxic for up to two weeks.
Those who were unfortunate enough to get stuck in the middle of all the radiation would either perish, depending on how much radiation they sustained, or they would suffer from radiation sickness and higher risks for cancer. The radiation would also have a good chance of impacting the development of offspring.
The best possible outcome is, of course, not to have a nuclear war at all. After all, the nuclear bombs that were dropped over Japan many decades ago were puny compared to the much larger bombs that exist today.