The dominant follical is the one readying itself for ovulation. Often, as soon as ovulation presents, a small cyst can form due to the eruption of the egg. These generally resolve without any intervention, though sometimes a birth controll pill may be prescribed if you form cysts frequently, if they become very painful, or do not seem to go away within a month or two. I would be more concerned with the pain you are now experiencing, which sounds like a possible kidney stone. I would ask to see a urinologist or nephrologist, or at least request an abdominal ultrasound for kidney stones. Most small stones also resolve (pass) by themselves, but it can be quite uncomfortable. You should also know what type of stone it is, so diet or medicine can help prevent recurrance. Good luck!