Hi, I Have A Hard, Immovable Lump On My Head

Hi, I have a hard, immovable lump on my head underneath my hair. it is behind my right ear, but raised a little so it is almost at the top of my ear. When i itch it, it becomes itchy, but if i leave it alone i do not really notice it. I am going to the doctor today at 3, but wanted to get an opinion on what it could be so i am not surprised.