Enable Docker port access only with Nginx reverse proxy

I have a Docker container on port 8081 running on Centos7, and a reverse proxy with Nginx.
My domain have a LetsEncrypt SSl installed and it works good when i access "https://my.example.com", it redirects me to my 8081 Docker.

But i when i access "http://my.example.com:8081", i still can reach my Docker application…i don’t want to enable this…don’t want to enable any http access.

I want to reach 8081 only through Nginx reverse proxy (that forces me to https)…i think it may be some configuration on my iptables, but i don’t have experience with it.
Can someone help me?

Thanks!

This is my conf.d file in Nginx

    server{
    server_name my.example.com;
    location / {
    proxy_pass http://localhost:8081;}

    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/my.example.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/my.example.com/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}

server{
    if ($host = my.example.com) {
        return 301 https://$host$request_uri;
    } # managed by Certbot

   listen 80;
   server_name my.example.com;
   return 404; # managed by Certbot
 
 
}