I didn't notice it yesterday, but today, at least, I saw a small purplish-pink lump on one of my rabbit's ears - looks like a sore. It's hard and seems to be on the outside of the ear. It's about the size of a small pea. There doesn't seem to be much fur on that one spot. Besides that, she's fine. I'm assuming this is an abscess? What can I do for her - short of taking her to the vet? Do I need to do anything? Just leave it alone?