Visit your domain /.well-known/nostr.json and verify that your npub in hex format is there.
In nginx, depending on how you're hosting your site, you can place a regular json file at that location in your domain's html directory.
Discussion
Got any tools to convert npub to hex? I wish nostr.json just used npubs.... More Nostr over-engineering and complexity.
https://nostrcheck.me/converter/
Npubs use the same scheme as Bitcoin addresses.
It looks fine, it worked when I used Apache, but now on nginx i got some issue make CORS working fine, looks fine now, but I does not know if it's enough to have validations here