Clearly it's time to buy a new disk and bring this one to the recycling.

And remember: "You only lose what you don't backup". The concequence is that you should backup everything you don't want to lose. It doesn't matter if it it's on an internal or external harddisk, an SSD, a USB-stick, a SD-card or a burned CD/DVD, it's the same for all media.

Not backing up only is an option for things you can so easily recreate or redownload that doing that is easier, takes less time or costs less money then doing tnat backup. The choice is up to you.