Your doctor probably saw a condition called spondylolisthesis, where one vertebra shifts foward. It usually occurs in the lower back. It can happen because of an injury or a problem in the joint between the vertebrae. It can also be the result of spondylolysis, which is a stress fracture in the bony ring that forms the spinal canal.
When spondylolisthesis happens in teenagers, the upper vertebra will sometimes slip completely off the lower vertebra. If you are an adult, chances are slim that the vertebra will slip completely off the one below. Your condition might not get any worse, but you are more likely to develop chronic back pain. It is important that you take preventive measures, including exercise and improved posture, to avoid problems. If your condition does worsen, surgery is an option. But you would be better off if you could avoid surgery.