I stepped on a pin. it punctured my heel. about half an inch went through. three days have past and it still sores. do i need a tetanus shot or wait?

Last tetanus was?: In general you need a tetanus (now TDaP)booster once every ten years. If you have a penetrating injury and your last tetanus shot was more than 5 years ago you should get a booster. I would not consider the injury you described as at risk if you stepped on a clean pin in your home, If you are still having pain, please be sure nothing was left in the wound, i.e. part of the pin.

See Your Doctor Now: You may need Tetanus Vaccine which is determined by 1) how long since you last had a shot and by 2) the status of the wound. Additionally, be aware that puncture wounds have a high risk of developing infection. See your doctor now for correct diagnosis and treatment of your wound and to receive your Tetanus vaccine booster if you are due.