What Causes Popping Sound In Lower Back With Pain While Weight Lifting?

Hi
3 weeks ago I was weightlifting and when I got the barbell to my shoulders my core gave way and I hurt the lower left hand side of my back. I couldn't sit up straight for the rest of that day and it hurt to bend. I rested for two weeks then went back training for a week. I've had no problems since until today. I bent down and felt a pop in my lower back. I now have pain in my lower left back and into my butt which goes around the side when I twist