certbot --nginx -d host.mydomain.com
Generation of a wildcard for nginx, it must include the domain with and without *.. You may even use same syntax
reported above but you probably already have an nginx http server in place.
certbot certonly --manual --installer nginx -d *.mydomain.com -d mydomain.com
Delete a certificate from local server, something usually stored in /etc/letsencrypt/live/
certbot delete --cert-name mydomain.com