Using nuclear weapons will likely trigger an equal response from the other side (NATO) and no one wants this. I could imagine nukes being used when enemy troops are approaching Moscow, as a desperate attempt to change the outcome of the war, or as a sort of mutual suicide like "if we die, you will die with us". However, Russia itself is not at risk now as this war is taking place in Ukraine.
Even in the case that Putin has lost his mind and gone mad, and he decides to launch ICBM with nuclear weapons just because he's having problems in Ukraine, he wouldn't be able to do it alone. I read just today that there are three chegets (Russian nuclear briefcases) and at least two of them are needed to command a nuclear attack. Putin has one of them, the others being in the hands of Shoigu and Gerasimov, and I don't think they are ready to die for a mad man.