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, the inspector's parents still live in Nirsk but have not heard from him for a while.
The inspector never seems homesick for Nirsk, and jokes that it is a "shit-hole" when reminiscing with Sergiu.