The chances of that happening are incredibly low. Even Putin knows it would mean the end of the civilised world as we know it.
Bear in mind that the powers that be are doing absolutely everything to avoid this while also trying to dampen Russia's actions.
Worst case scenario, OK, let's say it DID happen. You would either die very quickly or have to stay indoors for a couple of weeks while the fallout clears.
"Once we have ceased to see magic in the world anymore, we are no longer fulfilling nature's game of being aware of itself."