Oh, Cheeseboy - that sounds very painful!
Actually what you have described is an ilio-psoas bursa as in the attached image. Bursae tend to come and go which is why it seemed to get better and then come back. They are mostly self limiting which is to say they will usually resolve in time but it can be protracted. Sometimes the only recourse is to inject it with a steroid to make the inflammation calm down. But he wouldn't pop it because that's not the solution.
The reason it is affecting your back and feels like a nerve is knotted is because it is so close to the femoral nerve which is then getting involved in the inflammation. I would try taking some over the counter pills such as ibuprofen to help take down the inflammation. Exercise is unlikely to help.
But go back and hassle that surgeon. He has the solution in his syringe! Given the position, he will very likely to this under xray control to make sure he stays away from the blood vessels.
Hope you have success with him.