"Talk to Vernulus"

I just finished the quest where you have to investigate the hall of the dead. I killed the cannibal and thus failed the quest (on purpose).

The thing is, I still have the objective to "Talk to Vernulus" listed, even though that part of the quest is done with. Perhaps more strangely, whenever I'm in the entrance to Understone Keep, Vernulus is there, and he will keep following me and trying to talk to me, which is pretty annoying (there are no new dialogue options or anything. I can just ask him about Arkay and the Hall of the Dead, and that's it).

It's not exactly game-breaking, just a little annoying, so if anyone knows of a fix that would be great!

I have the problem where he keeps following me, so I just lead him into a corner and sprinted off and he stays there now, I don't know whether there is a fix