Go to the doctor and have the doctor get you on some AAS. It'll heal right up. An anti-inflammatory (short term) would be o.k., but, unlike any AAS, would be hepatoxic if in a pill form, where the AAS would not be, at any level. Back strains / pulls can take a long while to heal, especially if you're older. With the AAS, you'll be good to go right away. Nothing wrong with laying off, either. It takes about three weeks before you lose anything. In your case, where your weight is what it is, it would probably do you good to just rest, and gain some weight / recover. Because you're pictureless, there's not really much else to advise you on. The best, most safe, and fastest course would be the AAS. You didn't describe the type of pain, if any, that you're having. That would tell more about what's actually going on.
While you're at it, because of your age, you should have your testosterone levels checked as well. If they're at all low, or even moderate, it's time to start enjoying the numerous benefits of anti-aging therapy, and all the protections that it will afford you.