Ovulation day had an accident took plan b less than 16 hours later should i be worried?

Plan B: Plan B emergency contraception is a backup plan that helps prevent pregnancy when taken within 72 hours (3 days) after unprotected sex or birth control failure. The sooner it's taken, the better it works. It contains levonorgestrel, the same hormone used in many birth control pills, just at a higher dose. You are fine.

It won't harm you.: “Plan B temporary stops the release of an egg from an ovary. Prevents Fertilization. Prevents a fertilized egg from attaching to the uterus.” REF: http://planb.ca/how-it-works.html. Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy