It seems surprising that a scar would cause pain. Could nerves have been damaged? Or is the scar tissue drawing? I don't know if this will help you, but while taking large doses of vitamin B5 for a particular condition, I noticed that it lessened my scar tissue and some of it has seemed to disappear. You might try large doses of the vitamin (I was taking 1000 mg. daily), but you have to be patient for the result. There are no side effects.
Is the scar tissue internal or external? As Gym said, external scar tissue doesn't hurt, but internal scar tissue can cause inflammation to stay around and increase.