Two weeks ago, a guy friend tried to make me fall backwards. he pushed me back and downwards. i heard a pop and since then my lower back hurts a bit?

Back injury: A pop in the back as a result of an injury is not very specific in and of itself. It may be a sign of fracture but it may have been a sharp twist of a muscle or ligament. If your pain has been improving and you have no troubles walking, moving your bowels or emptying your bladder, numbness/tingling, i would watch and if completely cleared, no follow up is needed.

Back pain: Why would a friend do that to you? Anyway, you may have sprained a muscle in your back or you may have herniated a disk. If pain persists, see your doctor and he may order a ct or MRI to evaluate your back.