What would you expect someone to see if they scan the code and don't have a nostr client?

You could create a QR code that takes you to your profile on a particular website client like primal.net

That being said, unless you are face to face in the real world, qr codes are pretty inconvenient for sending over digital communications, just because we don't typically have the convenience tools to tap on a QR code and scan it, we need it to be outside the phone to be able to scan it.