If you're seeing HTTP 413 "Request Entity Too Large" errors in your nginx logs, most likely this is caused by file uploads larger than allowed by nginx.
To change it, add a larger client_max_body_size value to your nginx config. By default, the value is 1 megabyte. To change it, add (or, change, if you use this directive already) - here we allow 8 megabyte uploads:
client_max_body_size can be placed in http, server, location in nginx config.
Setting size to 0 disables checking of client request body size.