I dont find the comments that say "absolutely not", "its just scare mongering" "Putin would know that would kill him too so why would he?" Not remotely helpful.
The thing is, we don't know, and downplaying it just makes anxiety around it worse in my opinion as it screams in denial to me.
Since he has access to nuclear weapons, and has threatened the use of them, it does make it a real possibility, and I don't think denying that is helpful in this situation.
What is helpful is acknowledging it's a LOW possibility, and looking at actual reasons why its low possibility rather than just categorically claiming its empty threats.
I am far far far from an expert, but I've taken comfort reading the logistical issues with a nuclear attack, the fact that it would also be self sabotage, the fact that currently he has shown no actual desire to take this further than Ukraine (only mentioned nuclear as a retaliation).
I don't think it is going to happen, but I also acknowledge theres a tiny chance it could.
I'm sorry if this doesn't help, I'm anxious too and people just saying "it wont happen, chill out" doesn't help, but when the much more informed and rational members of mumsnet list the reasons why it probably wont happen with clear researched reasoning, I find that more comforting.