Security Certificate Error

I’m having problems connecting to HA from my PC via homeassistant.local:8123. Both Chrome and Edge initially block the connection unless you go to advanced settings and ignore the risk as they see it.
I think it is because I used to use DuckDNS for remote access and created a certificate via Let’s Encrypt. Chrome helpfully says " This server could not prove that it is homeassistant.local ; its security certificate is from mydomain.duckdns.org ."
Any idea how I can remove the old certificate and / or replace it?

You have probably inserted a ssl_certificate line in your configuration.yanl.