I found a hard bump on my skull right side by the middle of my ear any idea what it could be?

Mastoid process? The normal skull has a hard spike like projection located behind & at the level of the middle of the ear called the mastoid process. Multiple muscles dealing with the jaw attach to this projection. Other possibilities include lymph nodes located under the skin around the ear that vary in size from that of a pea to peanut. These are part of the bodies germ fighting crew & may enlarge when they are.