I did injure myself soon after resuming my workouts after a 4-month pause. I think I ruptered a disc in my lower back, though it was outside of the gym. What an easy injury! My left leg and the left side of my body hurt for a couple of days, then I started doing some exercises to fix my posture, and after a total of about 10 days I was completely pain-free. I wish brain injuries healed this fast too (still struggling with a concussion from 6 months ago).