Changed ECDSA host key even when I didn't manually change it? Database connection error

Hi, when I started and stopped my lightsail instance (linux), it says "Error establishing a database connection."

Upon further investigation, I saw:

[pem file]: Please contact your system administrator. Add correct host key in /Users/sid/.ssh/known_hosts to get rid of this message. Offending ECDSA key in /Users/sid/.ssh/known_hosts:3 ECDSA host key for braindocacademy.com.au has changed and you have requested strict checking. Host key verification failed.

I don't understand what's going on, and what steps I should take. I didn't manually change any keys whatsoever.

If you could assist me with this, it would be greatly appreciated. Cheers, Carl