Sounds like an ear hematoma. It's can be from a dog shaking it's head and it's ears flapping back and forth. It causes a broken blood vessel. Usually it requires surgery.
My Dog Has A Big Lump Inside Her Ear It Like A Huge Vessel Of Blood, What's Wrong?
Don'T haste go and see a vet as soon as possible cause it could be harmless but it could be serious don't take a risk take your dog 2 the vet