I'd add to that to copy all important files off immediately since if it is the "click of death" it could fail in seconds or weeks. Once it fails that's it, no more file recovery without sending it to a lab.
You can isolate the sound by removing the side cover and using a paper towel roll against the back or side of the drive to listen. If the sounds coming from the drive then follow the above advice, if not try and diagnose where the tick tick is originating. It could be a fan too.
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