Even before the pandemic I started to stock pile some things. I guess now I could last out for 3-4 month. It wont be nice, but doable.
Its not an easy task though. For one, it requires a extra expense, it takes some space in your house, and one has to concider the best before time span things have.
Especially food items are rather critical, as many of is only lasting for a short time. Especially fat and oil is problematic in that respect. Other things are much easier to store, especially dried stuff, like wheat, sugar, coffee, crispbread, dried beans and peas, rice, noodles ect.
Also lasting for years are canned (in tins or glasses) items. If they are canned properly, i.e. sterile. Also mineral water (sparkling) lasts several years.
Also a good idea is to stack some cheap booze and tobacco. It lasts forever and is handy if you need something to barter with.
Of course one has to pick a good storage place, too - dry, cool and dark if possible. And safe from insects. And finally: dont tell your neighbours about it. People can do crazy things if they are hungry, which you would never expect in normal times.
Btw., it doesn't need a nuclear war to paralyse a country nowadays. Cyber attacks can cause significant damage, too, and interupt power, water and traffic, thus causing shortages. So its also a good idea to stock batteries and power banks for emergency lights, mobile phones or radios.
I doubt Putin will play the nuclear card any time soon, because he knows that it means game over for him as well. But anything else you can expect from him.