Use the webserver’s access log (even a level above Nextcloud). There should be a lot of entries and you can just filter the access of a certain file. Here is a bit of background of the apache logs, what all the numbers mean: https://httpd.apache.org/docs/2.4/logs.html
From this document: 127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET /apache_pb.gif HTTP/1.0" 200 2326
You want to get the status codes 200, and the URL where your specific file is loaded.
As you see in the configuration, you can set it up a bit differently, mostly it’s similar to the combined log format. Nginx is similar, it might be different in some details, but the status codes etc. are the same.