In my experience, if there are no neurological deficits, they often do respond very well to rest and anti inflammatory meds. I had one this year who tweaked her back .. at first we thought it was a GI issue, but on close exam she responded the way that yours did when her spine was examined. She had no neurological deficits. She was on rest and meds for two weeks and is just fine now!
Once there are neurological deficits, I would be at a specialist in the blink of an eye. If a disc begins to impinge on the spine that is when issues begin and they can get much worse very quickly. Once it progresses to where there is no deep pain reflex, the surgery is less successful and often pups end up paralyzed.
I had a pup with two herniated discs in 2004. He quickly went down and was unable to stand up when I got him to Texas A&M. They did surgery and he recovered just fine and regained his ability to walk.
Back surgeries are difficult, but can be very successful...it often depends on what the condition is. I have a foster who already had diminished ability to function and it did not respond well to surgery...but her issue was not a herniated disc.
Good luck and please keep us posted!