Hi, 7Sinner. I must admit I had to reload the game to remind myself where you were (so many thanks for that
). At the top of the stairs, you should be able to turn left into another cavern tunnel. This has never been blocked on any of my playthroughs
I have a couple of thoughts. You may have hit a bug, in which case restarting from the last checkpoint usually does the trick. Alternately, have you picked up all the variations of the ShadowHand? It is possible to jump around and miss collecting some of them. The game may stop you if you haven't but that's speculation on my part. A bug is much more likely.
I hope this helps and good luck with the rest of the game.