Warlock Sidequest Bug - Should I start over?

[msmont]

There is an early sidequest where you follow a guy who is trying to kill a warlock.  They fight each other and you are supposed to choose a side and kill one of the two of them.  Well I accidently swung and killed them both.  Apparently if you do this the quest won't end as you were supposed to talk to the survivor to end the quest and they are both dead.  Well I should have reloaded my last save, but I didn't, I just kept playing.  I'm about 5 hours into the game now, should I restart the entire damn thing or does anyone think this is something they can patch retroactively so that the quest will mark itself as completed?  Feels like one of those things they can fix the quest itself for new people encountering it but not fix my situation.