Ibuprofen for swelling, paracetamol for pain-- hot baths
after a few days rest start stretching it out and doing light exercise like walking
id say after a week and hald when the pains gone-- do lightweight deadlifts of hyper extensions.
thats if the injury is MUSCULAR, if its a disc or ligament you need to seek proffessional help.

I tore my lower back years ago doing 550 lb deadlifts for 10 reps - felt a squealch.
immediately everything ceased up-- felt like somone had run across the gym and kicked me in the stomach, couldnt breath, talk properly.
took me out of action for months-- but exerciseing the injured muscle is a big part of recuperation.
start with hyper extensions, then 20 rep deadlifts, you`ll get back there, although saying that i never actually did get back upto 550 deadlifts every again afterwards

lower back injuries suck you cant get comfortable no matter what you do