Neck Lump, Whats wrong with my BP

[KMG]

Yes. I've seen it before.

What is inside the neck at this location?

If you knew what it was you should have let the OP know instead of offering what you did.

My thought was a rib could have been out of place.

A rib can pop out of place and is a fairly common sports injury. When it pops out many times it can be seen and felt as a bulge in the back. I don't know that it could happen in a snake but I don't see why not. It hurts when it happens.