The sciatic nerve runs from your lower back, down through the buttock to the leg, on both the left and right sides. Sciatica isn’t really a disorder itself, but a symptom of a problem, like the back pain you describe. If you have a slipped disk that is pressing down on a sciatic nerve root, this can cause the pain that you are feeling lower down.
There are several treatments that may help relieve sciatic pain, but since the pain is a symptom, before doing anything you should see your doctor. It’s not safe to assume that it’s your old back injury that is causing this problem because it could be something new. Some of the stretching exercises that work wonderfully well for some people can actually make it worse for others, depending on the cause.
Once your doctor has confirmed the reason for the pain, you might be treated through medications for pain and/or inflammation, physical therapy, back bracing, or even surgery.