I have a lump on my left buttocks that is severely painful and swollen and the pain has moved to my inner left thigh making it hard to walk, sit and sleep?

Likely an abscess: Sounds like you have an abscess. Without an exam I can't tell but from its migration it might be a peri-rectal abscess. These are legitimate emergencies and often have to be drained in the operating room. Don't wait till tomorrow, go the the emergency room now. If its a simple abscess they'll take care of it and send you home, if not they'll make sure you get the the care you need. Good Luck!