lower back isn't always about heavy --it's about how you lifted. I also had a bad back experience (which must've been my 3rd ever) a few weeks ago. I picked up a relatively light (10-20lb) object off my coffee table, but didn't really think about form at all, and next thing you know I feel that pain in your back that's bad pain. Took a week to go away fully.
Lower backs are all about giving them plenty of time to rest. Sleeping wasn't fun, lifting from almost any angle was out.
Just take it easy for a week or two (do something that doesn't involve your lower back --hard, I know) and if it doesn't improve, consider seeing a physician (I know wasabi and I both mean MDs).
Just don't rush into any back surgery. Most of the time they mess it up. Quick fixes are almost always disasterous with that part of the body. Because my dad's an orthopedic specialist, I promised him to never do any deadlifts, squats or similar when I work out. I do lower back extensions, but that's about it. No need for massive strength here.