Hello, you hurt your back at the gym when you were doing squats and heard a cracking or popping sound and has been hurting a lot. Well, when you say back that means area covered from neck to pelvis, which is obviously made of bones, muscles and other tissues. Most of the time back injuries can result from sport injuries or work around the house or in the garden or a sudden jolt after a car or bike accident. Usually it is the lower back is the commonest site for back pain and back injuries. It may result in the form of sprains and strains, herniated discs, fractured vertebrae. These injuries can cause pain and limit your movement. Most back pain goes on it’s own but it may take a while. In the mean time, you can apply ice, pain relievers and rest. In case if it is severe or does not get any relief from these, then you should seek your doctor to have a look to asses what exactly is causing you back pain and take appropriate measures. Hence it depends on the site involved and how much damage has been done and what kind of treatment that you should have; your doctor will do all these things after a physical examination.So it would be best to consult your orthopedician. Thank you.