According the Atkins a medium carrot will run you 7.3 grams of carbs, with 2.2 grams equaling fiber (so net carbs is 5.1 grams) I'd say limit your carbs for the rest of the day and for dinner. Good thing is you did it early, and you have the whole day to burn off those nasty carbs.

Just ran it through Fitday... a cupful is 11 grams of carbs, with 3 grams equaling fiber (so net carbs is 8 grams)