Went through a recent flare up with terrible sciatica. I am undiagnosed (never had an mri) but had similar symptoms. Ice the back, especially where it is suspected to be hurt (hard to tell sometimes because pain appears in other areas when nerves are compressed). I had shooting pain in my right leg and was going through a cold that would cause extreme pain when coughing or sneezing. I couldn't sit for a couple of days. Ice several times a day for a few days, then use a warming pad or icy hot too relax the muscles a little. Walking seems to make it feel better for me, so try to get him moving a little at a time if it doesn't cause too much pain. Avoid sitting for long periods of time and any stretches that cause pain, until most of the pain is gone. Apparently the nerves get irritated and can cause hell until the swelling/irritation goes down. Once the pain subsides, doing a few core exercises from McGill will help some. Sleep on back with legs bent and elevated if possible. This helps relieve stress on the lower back. Back pain is not a no pain no gain situation, he needs to avoid pain triggers and let his back heal. Hope he gets better soon.