What exactly did you try? Have you tried repairing the disk and repairing permissions?
Is it Yosemite or some other version of OS X? We can’t see your computer, so we have to ask.
Did you make system changes since last night, if so, what were those changes?
As requested please post the information about your system temporary directory: Audacity is Already Running glitch - #13 by Leland The Terminal is at /Applications/Utilities/Terminal.app.
Gale