Use command: gpg --list-secret-keys --keyid-format=long to list the long form of the GPG keys for which you have both a public and private key.
Use command gpg --delete-secret-keys zzzz to delete the GGP key id zzzz
Use command: gpg --list-secret-keys --keyid-format=long to list the long form of the GPG keys for which you have both a public and private key.
Use command gpg --delete-secret-keys zzzz to delete the GGP key id zzzz