had a scare as my puppy has a large lump on his head between his ears . it is soft  but pertruding sitting like a golf ball shape. he must have knocked while playing with his brother, as it is a haematoba, which all I have to do is leave it to go down as it will take a couple of weeks. this apparently can happen when they knock their heads hard. he is fine in himself. I read on here sometime ago that a vet sent a dog to a specialist surgery and by the time the puppy had a MRI scan etc, it turned out to be a haematoba. over a £1,000 later the treatment was to have left it well alone to begin with. That is not to say that all lumps on dogs should be assumed to be a haematoba, but to take a dog to another vet if you want a second opinion.  Haematobas are generally diagnosed easily, so the vet will know what the best course is, and one should always get it checked.

A haematoma is just a big bruise, like normal bruises it will take time to go down and the old blood be absorbed whilst it goes through all the colours of the rainbow on the surface if not totally obscured by coat.

You will have to breakup play before it gets that rough in the future or the injury may be worse

My youngest bitch had this, a more prominent occipital bone - then she liked to hide under things and leap up clonking herself.
Vet advised leaving it so we did, it took months rather than weeks but all fine now!