You need to describe this a bit better.
Is the pain on one side, both, or in the middle of the lower back?
Does the pain travel down the back of your legs (one legs, both legs)?
How old are you?
Are you male or female?
When I was around 19, I hurt my lower back. I was doing bent over dumbell rows (very heavy with your standard 19 year old piss poor form). I strained/pulled my sciatic nerve and literally had to be carried out of the gym. When I got back to my buddy's place (no way I could drive home), I took my shirt off and was black and blue from my mid back to 1/2 way down my right leg - I thought I did some major damage to my back.
I saw a decent chiropractor in the morning that fixed me up good.