This outlines an article which outlines how to rescind an earlier decision to take lower Social Security retirement benefits. By rescinding your decision to take early benefits, you can increase your retirement benefits -- but only after you pay back all your previous retirement benefits!
Note that we cover this same concept in this video.
The author of the article is plugging software (from $149) to do the cost/benefit analysis. The article is worth reading, and the software may be worth it as this can be an important financial decision.
Social Security Handbook