Ah, the blessed DL, again!.....people must understand that the DL is not meant for everyone who work's out, as the squat is not meant for everyone no matter how perfect their forms try's to be. Probably the prefered way of picking up a dead weight off the floor is inside a trap/shrug bar because the weight and the arms (acting like a cable during the lift) are along side the body and not in front which may cause a unnatural stretch/tweek to the small of the back, when that area is under great stress (weight lifted).
May want to take a couple of weeks off training to insure recovery. During that time it may be wise to see about a spinal adjustment or even a deep sport's massage if you have the extra bucks. May also want to try GoodMornings with just a light exercise bar (or even a broom handle!) every day (20-30 light, easy reps) to bring healing blood into the area and also to keep a somewhat flexable lower back area. Can even rub some sports lotion,cream, etc on to bring extra heat into the lower back while doing the light GM'ings. In any event rest will be the main requirement to bring that back area to a normal state again.
Personal note: I really prefer doing SLDL's rather than regular versions DL's, but just as low as the 45's allow. That lift is just about 100lbs lower than my regular DL and never have been close to injury while doing it. The back is keeped straight & flat throughout the lift. I find that SLDL's and GoodMornings (probably even more) have helped my squats greatlyand also give great core strength to total body. Good idea to work the abs strongly, just as hard as the back, each will balance the other out. Good Luck.