Nostr: Can I change my Nostr private key?

Short answer

A different private key produces a different public identity under Nostr's basic key model. You can create a new keypair and announce a move while you still control the old key, but existing signatures do not become signatures from the new key automatically. Move follows and profile details where your client allows, and tell people how to verify the new account.

Sources

NIP-01: Basic protocol, NIP-02: Follow lists.