The war between Russia and Ukraine has been going on for more than 1000 days and both sides are spending a lot of money on it and as a result, innocent people are losing their lives and fighters are being killed. In fact, war does not bring any benefit to humanity, yet the world is trying to find a solution through mutual war.
NATO is constantly providing financial and military assistance to Ukraine and Russia is demonstrating its strength with a single effort and is suffering a lot financially and militarily by waging a long-term war.
If Russia, which is facing financial and military losses due to waging a long-term war, gets annoyed and uses nuclear weapons, what effect could it have on the world ?
As a direct participant of the events (I am a citizen of Ukraine) I will slightly correct your introduction:
This is not a war between Ukraine and Russia, it is a terrorist attack by Russia on Ukraine. It did not start in 2022, but in 2014 after the invasion of Ukraine by the terrorist country. In 2022 Putin seeing impunity and lack of response from the west decided to “end Ukraine for good”. But. Ukraine became an “aspen stake” for Rashism.
Putin, realizing that he is losing the conventional war in Ukraine, realizing that there is no “great Russia”, no “second army of the world”, no “weapons that have no analogues”, decided to threaten a non-nuclear country with nuclear weapons! But we know the behavior of this “gopnik from St. Petersburg back alley”. He has drawn “red lines” 100500 times, which then turned from “red lines” into a brown bad smelling trail of Putin crawling away

Yes, he knows how to scare, but he is not an idiot and understands perfectly well that by starting a nuclear war, he will be destroyed and all his castles, yachts and other assets stolen from Russia will turn to dust.... And like all dictators, Putin is cowardly and wants to live. He and his tame dogs like Medvedev promise to “launch a nuclear strike on the EU and the USA”, i.e. on their children, wives, mistresses, who have long lived in the EU and the USA and not in the collapsing Russia !

The only real threat I see is the transfer of nuclear technology to such countries as North Korea and Iran, which most likely has already happened, when Putin humiliatingly begged them for missiles and “Shaheds” for the “second army of the world”.