Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
How long has he been showing these signs?
Does he itch, rub, or scratch the back of the ears?
Any changes to the skin (ie pustules, pimples, redness, crusts/scaling, ulcers, or sores)?
Any discharges or redness in the sore ear?
How much liver are you still feeding? How much does he weigh?
Can you take a photo of this? If you can do so, this will let me see what you are seeing. To post them online, you can use the paperclip icon on the tool bar above your text box. Or if you can't see that on your computer/phone, then you can post them on any other site (ie Flickr, Photobucket, imgur, etc) and paste the web link here for me to check.