If it activated (i.e. had swollen), then the nutrient pack inside the foil pack must have burst and fed the yeast. How much did the outside package swell? Significantly? You shouldn't have needed to have cut anything.
Regardless, as long as you scissors were sanitised, you'll be fine. There's nothing in that smackpack that can't go it the fermenter; although, the wee plastic bag that the nutrient was in doesn't need to go in.