When you delete a link, it is permanently removed from your account and no longer works when clicked. If there's a Bitly Code associated with it, the Bitly Code no longer works, either. If someone scans the Bitly Code or clicks the link after you've deleted it, they're taken to a Bitly error page.
Link deletion is permanent — neither the link nor the Bitly Code be recovered after the link is deleted. Be sure to confirm your Bitly Code is not actively in use (for example, on printed materials) before deleting the link.