Does anyone know what entry point a hacker could have if a sever's OpenSSL has been patched but a site's SSL certs have not yet been rekeyed?
If the remote attacker was able to retrieve you private key before you patched, then they can decrypt all any previous communication that has been performed if you didn't use perfect forward secrecy and perform man-in-the middle attacks. Intercepting and possibly modifying existing communications. They could have also captured credentials needed to remotely access and modify your system, or your user's accounts.
If you are lucky and nobody used this bug to collect your keys or anything else while you were vulnerable, you would theoretically be fine.