create subdomain on nginx

subdomaincreatenginx.sh

first setup A record on your domain registar
sub.yourdomain.in 1800 IN A 13.232.209.111
for this you can refer this link https://www.godaddy.com/help/create-a-subdomain-4080
record type: A
host: sub
point to : your ip address of the server.

now 
then create one directory /var/www/sub.domain.com
then create one empty file sudo nano /etc/nginx/sites-available/sub.domain.com

then add this lines
server {
        listen 80;

        root /var/www/sub.test.com;
        index index.html index.htm index.nginx-debian.html;

        server_name sub.test.com www.sub.test.com;

        location / {
                try_files $uri $uri/ =404;
        }
}



sudo ln -s /etc/nginx/sites-available/crm.webtomarket.in /etc/nginx/sites-enabled/crm.webtomarket.in

(optional)
then i think you wanted to apply ssl here also 
sudo certbot --nginx -d sub.domain.in ( do not write this -d www.sub.domain.in)
// this will write letsencrypt setting in /etc/nginx/sites-available/crm.webtomarket.in file now you just need to write php running script setting in it.
and all set.

best of luck