Thanks for the question.Getting a MRI of lower back is ideal step.This can help to plan appropriate treatment.But since you are having left arm symptoms as well you should also get a MRI of neck done.Your symptoms are because of a pinched nerve or lower limb radiculopathy (Sciatica ). Common cause is bulging intervertebral discs in the vertebral column that compress on the nerves as they come out of the spinal cord. Symptoms are experienced along the area of distribution/path of that particular nerve. From details provided and MRI findings its obvious that you have radiculopathy. The treatment vary from conservative to surgery. Conservative treatment include anti-inflammatory medications, physical therapy or chiropractic treatment, and avoiding activity that strains the neck or back. The majority of radiculopathy patients respond well to this conservative treatment, and symptoms often improve within six weeks to three months. If patients do not improve with the treatments listed above they may benefit from an epidural steroid injection. With the help of an X-ray machine, a physician injects steroid medication between the bones of the spine adjacent to the involved nerves. This can help to rapidly reduce the inflammation and irritation of the nerve and help reduce the symptoms of radiculopathy. In some cases the symptoms continue despite all of the above treatment options. If this occurs and the symptoms are severe, surgery may be an option. The goal of the surgery is to remove the compression from the affected nerve. Depending on the cause of the radiculopathy, this can be done by a laminectomy or a discectomy. A laminectomy removes a small portion of the bone covering the nerve to allow it to have additional space. A discectomy removes the portion of the disk that has herniated out and is compressing a nerve. I would suggest you to see a spine specialist who will take into account severity of your symptoms and MRI findings to guide about the treatment. Thank you.