Huh? You installed the left side before the right, and now it won't unscrew? Sounds like you stripped the threads. You'll need to push it from the right side with a screwdriver handle or something while you keep spinning it until whatever is left of the threads decides to bite and come out of there. Don't know if Miche offers left BB sleeves on their own. You may have to just buy another completely new one - and read the instructions before installing this time.