I tweaked my lower back yesterday doing squats... my legs are sore AND my lower back hurts now. I'm gonna need some extra rest days for sure.

I only get sore from doing squts if I haven't been doing them in a while, and it's not like I am lifting terribly low weights.

Try doing 3 sets of 5, that's usually more than enough to gain strength.

"Suffer now or suffer later". Swift recovery!