Nginx: site from internet and site from LAN?

Question

Nginx

There is a Debian 9 server with nginx + php-fpm on it.
Site config for access from the Internet:

user.site.com

server {
listen 80 default_server;
server_name user.site.com www.user.site.com;
return 301 https://$server_name$request_uri;
}
server {
listen 443 ssl;
ssl_certificate /home/back/ssl-key/mycert.crt;
ssl_certificate_key /home/back/ssl-key/device.key;
root /home/back/user.site/public;
index index.php;
access_log /var/log/nginx/site-access.log;
error_log /var/log/nginx/site-error.log;
location / {
try_files $uri $uri/ /index.php?$query_string;
}
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/run/php/php7.3-fpm.sock;
}
location ~ /\.ht {
deny all;
}
}

Config for access from inside:

admin.site.com

server {
listen 80;
server_name admin.site.com www.admin.site.com;
return 301 https://$server_name$request_uri;
}
server {
listen 443 ssl;
ssl_certificate /home/back/ssl-key/mysert.crt;
ssl_certificate_key /home/back/ssl-key/device.key;
root /home/back/admin.site/public;
index index.php;
access_log /var/log/nginx/site-access.log;
error_log /var/log/nginx/site-error.log;
location / {
try_files $uri $uri/ /index.php?$query_string;
}
location ~ \.php$ {
include snippets/fastcgi-php.conf;
fastcgi_pass unix:/run/php/php7.3-fpm.sock;
}
location ~ /\.ht {
deny all;
}
}

The user.site.com site works, but in order to access the admin.site.com site, you need to edit the hosts file and add:

hosts

local_ip_addr admin.site.com

Actually, the question is: is it possible to configure nginx in such a way as to avoid editing the hosts file?