Nix search path entry does not exist

[KaiserKarel]

I'm getting the following error:

warning: Nix search path entry '/nix/var/nix/profiles/per-user/root/channels/nixos' does not exist, ignorg
warning: Nix search path entry '/nix/var/nix/profiles/per-user/root/channels' does not exist, ignoring
error: file 'nixpkgs' was not found in the Nix search path (add it using $NIX_PATH or -I), at /home/karel3

Any advice on how to use nix build inside the vm?