I've done this before using a PowerShell script that was scheduled to run daily by Windows Task Scheduler.

Unfortunately Power Shell is not available for us to run   Thus, I was hoping it might be accomplished within Nintex..

I've also used this action ‌ that runs powershell in a workflow. But there isn't an action I find that directly queries a file share via a workflow.

I am facing similar task, where a CVS file gets downloaded from SAP with a lot of information which then is needed to be  updated into the Sharepoint List with relevat data only e.g. Holiday Balance etc.

I been thinking about how to tackle the task :/