TMI: painful lump in butt cheek

I have had a painful lump in my butt cheek for about two months now. I was embarrassed to get it checked out but now I'm scared and have anxiety. I am afraid that it will be cancerous or something. At first it only hurt when I touched it. Now it hurts to walk and sit. What could it be? I'm really frightened to go to the doctor and haven't even told my mom about it yet. (I'm 17)