Wow, I wish that I had some piece of knowledge to offer, but that is strange. Hopefully someone with more experience will see this thread.
My first thought was possibly a stuck urate, but not that high up on the spine. The only thing I can suggest is having a vet check it out to see if it is some kind of tumor or subcutaneous lesion or abcess.
You can also try posting the pics over on Redtailboa.net. I'm sure some of the people there will have some ideas and suggestions. Good Luck!!!