What Causes Severe Pain In The Lower Left Back And Leg?
I read your question carefully and I understand your concern.
From a diagnostic point of view the MRI is the best diagnostic test to determine the diagnosis, so since it has confirmed a pinched nerve that should be the cause.
First step in management is always physical therapy and pain killers. Pain killers are anti-inflammatory medication used over the counter like Ibuprofen or medication for chronic neuropathic pain like Gabapentin, pregabalin or amitriptylin.
If those do not work and the pain persists then the next step are local injections of steroids and analgesics.
When those do not work either then I am afraid the last resort is surgery to remove the source of the pinching (usually a bulging disc or bony spur due to arthritis).
I remain at your disposal for other questions.