Show real IP of visitors

I installed Hestia CP on a vps server, everything is running fine, I just have a problem with allowing visitors from certain IP on a single website.
I tried to use htaccess and adding the lines

order deny,allow
deny from all
allow from my IP 

But the problem is that since the website is proxied through Nginx - all requests appear as coming from the server’s main IP, thus I can’t filter access based on IP.
Do you know how can I disable this or make that it will show the real visitors IP addreses ?