Knowledge bump on my dogs head? ?

Was the bump always there? The fact that you see a bump that is changing does not sound like it's the normal anatomy of the dog unless the dog's head is swelling. I'm sorry to say this but my only advice can be to see a vet. Is it normal? Absolutely not if your dog's head is changing in size. Is it serious? We have no idea. So unfortunately we can't answer your question. 

The occipital obviously all dogs have them no matter which breed its a part of their bone structure ya see... Ita the first time I've read of it described as a... knowledge bump.. though 

I do not know WHERE you got the term, "knowledge bump" yet could not find the CORRECT TERM => Occipital bone.  Many (if not all) dogs HAVE one, it may be more obvious on a tighter skinned, single coat dog - such as yours.  

If your dog has an occipital bone that gets larger and smaller - THAT is NOT normal.  It would suggest to me he is HITTING or bumping that bone INTO something often (like crate frame or crate roof) or some piece of furniture and causing bruising and SWELLING.  You or you and your vet need to figure out how/where he keeps HITTING his head & stop that by padding - whatever.

Every dog has that protrusion.  It's part of the dog's skull.

Here's my concern - if it gets bigger and then smaller, who wouldn't you consult with a Vet instead of asking strangers on the Internet who can't examine the dog?

I know you don't want to hear "go to the Vet."  You'd rather guess at the problem and hope it's not a tumor or some other serious problem.

I hope your dog isn't suffering while you defend your "no Vet" position.

Good lord!  Its the occipital bone - something every dog in the world has.