You need a computer on the internet. If you are happy to host the website on your own existing internet connection, you can download, configure and install NGINX on any computer on your network. You will need to set up port forwarding and ensure that the computer hosting the website is on 24/7/
Likely, you will also need to use a dynamic DNS service as home internet connections do not have static IP addresses.
Alternatively, (and this is what I suggest) you can buy a VPS for $5 a month and save all the hassle