I am surprised by your post. Russia very carefully tested the West's commitment to Ukraine, a fellow European country, by axing Crimea without any retribution, which turned out to be a staging post for a full invasion.
This 'accident' has all the hallmarks of being a similar strategic policy, of testing Nato to see if there is a response.
Russia have indeed threatened for some time, many months that a nuclear strike on Ukraine with targeted weapons was a possibility. Do you imagine they were just bluffing or lying? Based on what evidence?
We can not assume this was an accident
We can not assume that Russia intended to hit Poland
In the same way we can not assume Nato will do nothing
The facts are Poland has been hit - two people have died.
World wars started over much smaller infractions. You are mistaken if you can not see the risk now.