how to block external request coming from proxy server to nginx webserver

I have web application hosted in nginx web server. I would like to disable request from any proxy server to my webserver (nginx) .

I need to return 403 for those who request via proxy server.

Is there anyway to check X-Forwarded-For set in the request and not allowed those request from nginx ?

or any other way to achieve this ?

upstream tomcat_srv
{       


      server 127.0.0.1:8080;
      server 127.0.0.1:8081;

}

server
{

        listen  443 ssl http2;

        add_header   X-Content-Type-Options nosniff;
        add_header   X-Frame-Options DENY;
        server_name exam.test.com;


        ssl_certificate /etc/nginx/ssl/test/ssl-bundle.crt;
        ssl_certificate_key /etc/nginx/ssl/test/test.com.key;
        ssl_session_cache shared:SSL:10m;
        ssl_session_timeout 5m;
        ssl_prefer_server_ciphers on;
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
        ssl_ciphers ALL:!aNULL:!KRB5:!PSK:!MD5:!ADH:!eNULL:!LOW:!EXP:RC4+RSA:+HIGH:+MEDIUM;

        if ($http_x_forwarded_for) {
            return 403;
        }


        location / {
                proxy_pass http://tomcat_srv;
                }


}