Finally. Anyone running iOS 16 (or macOS Ventura, for that matter) can edit or undo iMessages they send in error. When you send an iMessage, you have 15 minutes to edit it, after which time the message will lock itself in. Be warned, though: Any edits you make will be visible in an edit history available under a convenient “Edited” tag, so this feature is best for making small corrections you’d usually fix with a follow-up message.
If you’d rather cover up a message entirely, delete it instead. You have two minutes after sending a message to remove it from your device and the devices of others in the chat. Of course, they have the same power, too.