I have had two Aural Hematomas.  They continued to swell to the degree
that the ear canal was sealed off.  As far as I know there is no
effective treatment without surgery.
 
I tried compresses, medication, then had the ear opened up and drained
along with medication.  There was no lasting improvement until the vet
did a full suturing/quilting procedure.  First she tried only two or
three stitches but that was not enough.  Ended up having to do about 12
stitches.  As the ear swells it separates the cartilage or something like
that and damages the ear to the point that it becomes a cauliflower ear.
If you treat it properly you will have minimal evidence of the trauma.
 
I also originally thought that it was from a bite.  One vet said a bite,
another said an ear infection causes it.
 
Best of luck.
[Posted in FML issue 3875]