Temurkhon
considered that "nor" can be used only in "neither....nor" construction.
Experts, please comment
I went ahead and Googled the concept of using nor without neither.
The following quote from grammar girl website clears the construction required for this:
“Nor” doesn’t necessarily have to appear in a sentence with the word “neither.” “Nor” can start a sentence. For example, if you’ve just mentioned that you don’t usually wake up at 6 a.m. and you want to continue being negative, you can start another sentence with “nor”: “Nor do I like to wake up at 5 a.m.” Another option is to combine the two negative ideas into one sentence and then start the second part with “nor”: “I don’t usually wake up at 6 a.m., nor do I like to wake up at 5 a.m.”
So it is the construction that's considered correct with the usage of nor in a sentence as is the case in this question. One just needs to be familiar with this I guess.