I don't understand. How did helping the old lady cause the broken glass to cut your tire? Maybe it had nothing to do with her and, by helping her, you gained enough positive karma to prevent the glass from puncturing your tube.

If, with your tire fully inflated, you can't feel a bump or a blister on your tire, then you haven't cut any of the caseing cords and I wouldn't worry about it. If you can feel a bump, I'd keep it on the rear because I'd rather have a rear tire blow out than a front.