A few months ago DD was hopping her Rody pony down the hall, tumbled off and started screaming. If she didn't point out that her ear was injured, I probably would have thought she had banged her head on the wall. Her ear looked red, and tender, she must have hit it on the baseboard, but not bruised. During the next few days a dark purple bruise appeared, similar to what you described, on the outside and inside of her ear. It took at least two weeks for it to totally go away, and it never went through the normal color changes, just slowly faded away.
HTH, DH who by no means has any medical training
thought it took so long to fade because it's mostly cartilage so less blood flow.