Back mri was 'negative' so what the doctor is saying?

No obvious problem: The physician most likely means there is no significant findings like a tumor, infection, fracture, disc herniation, or spinal stenosis. It means the differential diagnosis of possible causes of your back pain has been narrowed done by eliminating the previously mentioned diagnoses. It does not mean that other tests should not be done or that surgery or pain management procedures may not be need.

Nothing surgical: A spine MRI is a test that, if negative, definitively rules out potentially progressive or permanently impairing conditions such as nerve compression, cancer, infection, or significant fracture. A negative MRI means surgery is not a good option to treat spine pain. It does not mean that there isn't severe pain that should be addressed with means other than surgery.