If you change the password for one of your social profiles or a token expires, you will need to reauthenticate (or reconnect) the social profile to your CoSchedule calendar. This will not harm or affect any messages you might have scheduled to be published to that account. If you have messages that have failed due to reauthentication errors, those messages will need to be rescheduled.
To reauthenticate a social profile, go to the Settings > Social Profiles page. Any social profile that needs reauthentication will show an orange RE-AUTH button in the connected list.
Deleting is less fine.
If a social profile requires reauthentication, do not delete the social profile. If you delete a social profile from your calendar, any scheduled or previously published messages associated with the social profile will be deleted. This action is not reversible.