When you edit nginx coniguration file, it is better to test the new config file before you restart. This can be done with command

nginx -t

Example

root@ip-172-31-0-223:~# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
root@ip-172-31-0-223:~#

You can also use command

service nginx configtest

See also nginx