it can easily tweak the lower back. lower backs are the worst. mine wasn't injured perse, but those muscles tightened. makes you feel old as shit. everything becomes difficult. it wouldn't normally show up til a day or two after the tweak.

for me, it means not doing the free weight squats. I would do a bunch of stretching for the lower back. I'd do some back extentions. for squats, I'd go to the squat machine that would force my form, but still allow me to get low. this would help me with stretching that muscle too.

aside from any of that, I'd suggest resting before getting back into the gym. backs are nothing to play with and you could run the risk of a more severe injury by going back too soon. resting will give you a chance to see how sore you really are.