Two nginx server blocks on same port

In my point of View, it does not make sense to use 2 Blocks, if you want /app only accessible from 127.0.0.1 you can use allow to restrict it and use only one Block to serve it all, as I understand it correctly your request since its generic.

Server {
    listen *:80 default_server;
    location /app {
        index index.html;
        alias /var/www/app;
        allow 127.0.0.1
        deny all
    }
    location /static {
        alias /var/www/static;
    }
    location / {
         include     /path/to/uwsgi_params;
       uwsgi_pass  django;
    }
}

Since I don't have much Information, where "django" should be defined, I keep this as a generic solution for your currently generic question.