Nirsk is a village in Arstotzka. It is never visited or seen in the game but is talked about on a few occasions. The inspector was born and raised in Nirsk, as was Sergiu, and it is implied that the inspector only left Nirsk after being assigned to the checkpoint. According to an elderly woman encountered on day 19, at least the inspector's father still lives in Nirsk.
The inspector does not seem homesick for Nirsk and jokes that it is a "shit-hole" when reminiscing with Sergiu.