Usually there is a reason the dog was shaking it's head BEFORE the hematoma happened. The hematoma is usually the result of excessive head shaking. It won't usually go away for long until the underlying problem is addressed- even with surgery. Foxtails and ear infections (yeast or bacteria) are the usual culprits around here, but ear mites are also possible- but not very common in dogs. Chiggers/harvest mites sometimes. So the vet visit will be very helpful finding the underlying problem, and they may recommend draining the hematoma, or surgery, or putting in a cannula, or wrapping the head. The average dog needs an ecollar to make them leave the wrap alone. An ear hematoma is not a life threatening problem- but it is uncomfortable, as is the infection (or whatever) that caused them to start shaking their head in the first place...