it may be eczema,it depends if its dry and it may crack slightly. you might want to try Betnovate ( a vasoline type based lotion)
You should get your ears tested at a hospital by a professional.
its just where the skin has healed, its like a scar, some scar's are hard It could be that, or the ear is infected and it's a small ball of puss. What you do is you keep the earring in but twist it and clean it regualrly.
small bumps along hairline
I'd think not. But I could be wrong. ;)
a couple of days
Bunnies don't naturally have ears on their backs. If a bunny's ears are seemingly on its back, it could be due to a genetic mutation or a costume/accessory that has been placed on the bunny.
There are different degrees of 'backwards'. If his ears just flick back in a relaxed manner he is listening to something behind him. If his ears are pinned back flatter on his head he is sending a warning that he is not happy. It could result in a bite or a kick so when you see his ears like this be on your toes.
It is true that a rabbit's ears will go down when they are scared. So that isn't wrong.
It is a slim possibility. If the bumps get worse, seem to bother the cat, or do not go away in a few days contact the vet.
they are big.
Sounds like it could be a reactive dermatitis. Try changing your shampoo and or laundry detergent.
I lived in Scotland for 3 years and many people in Scotland have ears that could be pinned. I personally think that it can be very sexy.