If you are wrestling with something thoroughly illegal then trying to forget it may be harder, especially if you caused identifiable suffering. Only you know what it is and only you can deal with it.
If it was nothing illegal but involved interaction with or effects on someone else then and someone suffered and/or was hurt then perhaps you should consider tackling/confronting the individual(s) and the issue itself. Only you know what it is and only you can deal with it.
You need to weigh up whether your current discomfort is better than whatever consequences would result from bringing this into the open. I would always be inclined to hope for empathy from others, but then again that hope does not always look that hopeful (if you know what I mean). In your case it is weighing up discomfort/fear against the hope of getting rid of it no matter what follows. Presumably someone already knows or else someone might discover.