Don't hate yourself! First off, I'd say that lots of women who belong to this forum have cheated with chocolate during their time of the month, myself included!
Don't beat yourself up over it. What you did isn't good, however, it's not life ending (or even diet-ending!)! If it kicked you out of ketosis, I believe that carbs stay in the body approximately 48 hours (varies from person to person), so you should be back in ketosis in a couple of days.
I'm not sure if LC'ing makes us crave chocolate and sweets even more during our TOM or not. I always craved these things during that time, long before I ever started LC'ing. What I do now is (if I'm craving really, really bad) buy a sugar free, low carb chocolate bar, like Russell Stover's or the various brands of LC stuff sold in grocery stores. They totally satisfy my cravings, and while some people say sugar alcohols found in this candy isn't good for you, I say they're not as bad as eating real chocolate. If you're still in induction, though, you should probably avoid the LC stuff...at least until you move into OWL...
Tomorrow's a new day...actually, every second of every day is a new opportunity to start anew...so just put your mistake in the past and commit yourself to not doing it again.
Best of luck.