Avoid admin panel visibility to the world

Hi all,
I have already set up the Matomo server service behind a nat, and the FW will port forward the JS to the server in local lan. However to raise the security bar I would like to know a method to hide/block any access from the Internet to it…Is there any already method to achieve this?
I assume the data collection is hugely sensitive and there must be a method to bar this.
Can you please help?

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