If you look in the error log from your site
2015/01/25 13:01:31 [error] 7477#0: *11490 client intended to send too large body: 1424254 bytes, client: 2a02:168:66b9:0:dc3c:5449:d617:86f6, server: www.safematix.com, request: "POST /wp-admin/async-upload.php HTTP/1.1", host: "www.safematix.com", referrer: "https://www.safematix.com/wp-admin/post-new.php"
Open the nginx.conf and edit the http tag
vi /etc/nginx/nginx.conf
http {
client_max_body_size 50M;
...
...
}
It is also possible to put the settings per location tag.
location {
client_max_body_size 50M;
...
...
}
Don’t forget the reload from the nginx service.
service nginx reload