Other answers have only called out rotating the secret which is how you fix this specific failure. After you’ve rotated, delete the key from the repo because secrets don’t belong in repos. Next look at something like git-secrets or gitleaks to use as a local pre-commit hook to help prevent future failures. You’re human and you’re going to make mistakes; plan for them.

Another good habit to be in is to only access secrets from environment variables. I personally use direnv whose configuration file is globally ignored via the core.excludesfile.

You can add other strategies for good defense-in-depth such as a pre-receive hook checking for secrets to ensure no one can push them (eg they didn’t install hooks).