nginx: [emerg] "user" directive is not allowed here in /etc/nginx/conf.d/nginx.conf:1

[IavTavares]

I've dockerized a Flask+Gunicorn+Nginx app.
When I run Nginx in the docker's image bash, by running /usr/sbin/nginx, I get:
nginx: [emerg] "user" directive is not allowed here in /etc/nginx/conf.d/nginx.conf:1

I'm running from an Nginx image.

The file nginx.conf has the following code:

user  nginx;
worker_processes  auto; 
# auto When one is in doubt, setting it to the number of available
# CPU cores would be a good start (the value “auto” will try to autodetect it).
 
error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;

https {
    upstream app_name {
        server web_1:5000;
    }

    server {

        listen 80;

        location / {
            proxy_pass http://app_name;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Host $host;
            proxy_redirect off;
            proxy_set_header   X-Real-IP            $remote_addr;
            proxy_set_header   X-Forwarded-Proto    $scheme;
        }
        
    }
}

Note:
Running find -name "nginx" in the docker image, I get:

/etc/default/nginx
/etc/logrotate.d/nginx
/etc/init.d/nginx
/etc/nginx
/var/log/nginx
/var/cache/nginx
/usr/lib/nginx
/usr/sbin/nginx
/usr/share/doc/nginx
/usr/share/lintian/overrides/nginx
/usr/share/nginx

[IavTavares]

The problem is that there's already another file /etc/nginx/nginx.conf, which is including these variables, and the configuration in the file /etc/nginx/conf.d/nginx.conf.
I need to remove

user  nginx;
worker_processes  auto; 
# auto When one is in doubt, setting it to the number of available
# CPU cores would be a good start (the value “auto” will try to autodetect it).
 
error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;