Dynamic Wildcard Server Name on Nginx Block

nginx.conf

server {
    listen 80;
    server_name ~^([\w-]+)\.YOURDOMAIN\.com$;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;

    server_name ~^([\w-]+)\.YOURDOMAIN\.com$;
    ssl_certificate /etc/letsencrypt/live/YOURDOMAIN.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/YOURDOMAIN.com/privkey.pem;

    location / {
        proxy_pass https://YOURBACKENDSERVER;
        proxy_set_header host $host;
    }
}