Depends on exactly what it was that was cutting me about it.
I would hope I would admit that there was something wrong with the descision, or at least that the outcome was not intended. Depending on exactly what it was, make amends or make peace of some sort. It really would depend. Mostly try to figure out what it was that was wrong for me and what options I have. Usually easier said than done. If it was at a more introverted time of my life I would twist it arround in my head and obsess over it until I was tormented enough by it to deal with it appropriately. I don't recomend this version. Cut yourself some slack if you can: whatever it is, you are human and people make mistakes.
If it isn't too personal, a few more details would make it easier to give more direct advice.
Whether or not you want to tell us, there is a lot you can think about. It is obvious that whatever decision you made isn't sitting well with you. Do you know what it is that is hurting you about the decision? A wrong decision you feel bound to? One that is right but has unentended consequences or requires something painful? Something was right about the descision... What was it you wanted to have happen when you made it?
"There's not much that's contrary to nature if you just know how to coax her along a little."- Mad Amos Malone (A. D. Foster)