Greetings and salutations,
If you were using Apache before switching to Nginx, then the problem is easily solvable. Mainly, you need to tell Nginx which sites to enable and which ones to disable access to. The configuration is different, and not compatible, with Apache, but it is just a matter of auditing a couple of configuration files.
If you are interested, please send me a message and I will get back to you as soon as possible.
Until then, best regards.