I agree with LS and justme, you are going to be fine and its good to allow yourself some indulgences. Try not to feel so bad it is actually good for you
About what happened to your body my guess would be that you were just not used to that kind of food, b/c you said you have been working out and watching what you have been eating. So your body prolly had to work a little harder to process it but no big deal. Also a lot of the symptoms could have been created in your head, you know from feeling so bad about eating it, I know I have done that!!
No worries Smags, just jump right back on track and try not to skip meals, what you ate was good for ya and perfectly normal