I realize that it is difficult to adequately describe an injury over the internet, yet I will attempt do to so as clearly and precisely as I can.

Yesterday, in my second set of deadlifts, I hurt my lower back as I lowered the weight to the floor for the second rep. As far as I can tell, a combination of leg soreness and general fatigue caused my form to suffer; my lower back became arched and bore the brunt of the weight. Almost immediately, I noticed a sharp pain in my lower back, just above of, if not at the same level as, my waistline. It is a sharp, singular pain; it isn't diffused throughout the muscle. Rather, it seems to be concentrated in a single point. There is also a large degree of stiffness associated with the pain; it is difficult to bend my back past a certain point.

Any ideas as to what this may be? It is not an unfamiliar pain, as it has happened before, but it has never been this serious. For a while, I plan to take the following steps: take it very easy on any exercise which significantly stressed the lower back; abnegate deadlifts entirely; and focus on core-strengthening exercises.