Bump on ear

I recently discovered a huge bump on my cat's ear. The bump is hard but not too hard. He acts as if it doesn't bother him but it looks uncomfortable. He scratches or holds his head down whenever I touch it.

It looks like an ear hematoma, basically subcutaneous bleeding which can be caused by ear mites or a trauma of some sort.  It isn't difficult to treat but it must be treated or things will likely get worse, and right now it can be addressed much more cheaply than if you wait.

See this link and please consult a vet.

http://www.petmd.com/cat/conditions/ears/c_ct_cat_ear_hematoma