From your description of the pain radiating down the quadricep, this is not Sciatica. The sciatic nerve travels through the gluteus maximus and down the back of the leg. This sounds like the saphenous nerve. Pain can originate the lumbar region as you describe. Usually is due to inflammation in the nerve sheath and the anti-inflammatory agents you have been prescribed will help the most. Stretching may actually make the inflammation worse due to irritation of the nerve sheath. I would recommend rest and the anti-inflammatory drugs. If this does not resolve in a few days or keeps recurring, I would recommend an MRI. Could be a herniated disc or synovial cyst impinging on the nerve.
Disclaimer: I am not a physician, but I do stay at Holiday Inn Express on a regular basis
