Impossible d'envoyer un fichier au serveur avec nginx

Your nginx worker has no permissions to write in nginx directory.
so you have two options:

1. give the nginx permisions:
  chmod -R 777 /var/lib/nginx/
  
2. change the nginx user to nginx(better option).
  go to to /etc/nginx/nginx.conf
  and change the user to nginx.
David Diamant