I'm in the process of dealing with the nightmares too. The last time I tried to quit drinking, it was these nightmares that made me start again. It seems almost silly that a nightmare would be enough to make someone keep up an addiction, but the nightmares are SO awful. So so awful. They seem to come from what you fear the most and are "catered" exactly to what is going to grasp your emotions and psyche for days.
I have been sober for 2+ days this time, and last night was my first withdrawal nightmare... They always have something to do with a medical clinic (I am a med-student and currently work in a clinic), and they always involve the scariest and worst possible situations with patients that my brain can imagine. The withdrawal from alcohol seems to "know" exactly which buttons to push in my dreams to get to me. I really hope they only last a few nights.
Good luck... hang in there. Just know that tonight I'll be going to bed scared too, but we're not alone in that.