The first room of the tombs has a broken wall/passage into the one with the barred door. Use your torch and you'll find it.
(There's also a useless clue there!)
Try each room again and search the rear right corners (relative to the entrances to the room).
You should find a way into the room you couldn't access.
You probably figured it out, but that torch does flame damage to the skellies. If you're evasive, you can kill 'em all with the torch.