Once a nuke is used we’re all dead, it doesn’t matter where. In this case the nuke would destroy Russia itself just like it’d wipe us from planet earth. The fear of nukes is being used to scare us into submission, while we’re forgetting the implications of nukes.
Regardless, drones have reached Moscow. If they wanted to nuke they would have nuked already. What is more likely going to happen is that more Russians will be sent to war.