Physical errors indicate that a drive is failing, and it’s definitely a bad sign that chkdsk wouldn’t run at startup.
If I were you, I would back up anything you really, really need right now and then work on getting a new hard drive pronto. Also make sure to save any new and important files to some sort of removable media.
It sounds a lot like this hard disk is failing, but when it will actually go catastrophic is hard to say.
Hard drives are mechanical devices, and are usually tested and rated with an MTBF (Mean Time Between Failures) rating. This is the average time that a drive will operate before failure, but it doesn’t mean that a drive will definitely last that long before failure. Some fail much earlier, some after a couple of years, and some in the very first days of life, while some go like the Energizer bunny (I once had a hard disk that ran continuously for seven years before failing).
I can’t stress the importance of backing up your data enough. If you have not already done so, do so now, as it’s impossible to tell whether this drive might catastrophically fail tomorrow or last another year. To be safe, I would replace it. If it’s under warranty still, contact manufacturer.