What Causes Recurring Lump On The Lower Back?

Sure, as you know there are supposed to be 2 dimples on the lower back. On the right side I have a knot over one. There are plenty of ways to relieve the pain, but are there ways to speed up a healing process? Is there anything I can do to prevent this knot from coming back? Could you tell what I could have done to my lower back to create this knot ?