I think all the fearmongering over use of nuclear weapons is simply western way of painting Russia as completely unhinged.
In Russia itself there is more popular will to drop nukes on US itself or their vassals for supporting Ukraine, rather than on Ukraine. Plus, you going to deal with radiation from the nuke if you drop it on Kiev.
Rattling from the West and Russia is to be expected. It is a natural tactic to threaten the use of something as a deterrent to the other party not yielding, so on the face of it - yawn.
However, more interesting is the actual use of a small weapon in Ukraine rather than some swarm launch at everybody. The use of a singular weapon in the Ukraine is an interesting concept insofar as it is an event that can be contained and would not have to result in a Nuclear war across the globe.
The scenarios that unfold are fairly vast; but I do not see any of the scenarios that unfold would be to Putin's benefit - unless his goal is to indeed lock his country into a hermit kingdom and rule the decimated economic wasteland that would ensue. In that case, unloading on the Ukraine could achieve that if that is indeed what Putin wants.
If Putin or anyone else thinks that the threat of deployment or the actual deployment of a small weapon of such would actually make Europe and the West pull back, the exact opposite is true; and so for that reason I do not think that is his goal at all. Putin is giving NATO the unique opportunity to expand it's horizons vastly and we could see a number of countries jump onboard with NATO quite rapidly.
On a more conspiratorial note, the world is drowning in debt and wars have a great way of redistributing the burden towards the losers; and often in history, wars have been preceded by economic events not too far off from what the Globe is experiencing now; which I do not mean to allude to some masterplan but more or less to be a natural human progression from what was predicted when the COVID virus first emerged, in that it would in a world already attempting to push through the glut of 2008, could be in theory pushed into a no-win scenario with debt as a result of increased government spending and inevitably result in the split of globalism.
Whatever scenario Putin imagined that would somehow result in a stronger, united and financially more secure Russia from this invasion seems to be pie in the sky. And a launch of a singular weapon or the threat of such is not going to get him any closer. If he launches a singular weapon I do not see a nuclear war as a result. Don't ask me what happens though if he is brazen enough to launch 2 or more, then I think the response is inevitable as well the result for us all.