I want to set up an nginx reverse proxy behind a NAT. It will proxy multiple internal servers to the outside world. ALL services will run on a non-standard port (i.e. not on 80 or 443). nginx will also do the HTTPS encryption for the internal servers which use HTTP. For that I want to use Let's Encrypt with certbot. Therefore I need to allow connections on ports 80+433 to nginx.
Is there a way to block any access to these ports apart from when certbot renews the certificates? As stated before, these ports are not used for anything else.