Ghost in a subdir

ghost.txt

# Nginx location:

location ^~ /blog {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_set_header X-NginX-Proxy true;
    proxy_pass http://127.0.0.1:2368;
    proxy_redirect off;
}

# Ghost config:

production: {
    url: 'https://www.yourdomain.com/blog',
    mail: {},

    ...
}