Stepped on a rusty nail but i don't think it punctured my skin. should i be ok or be heading to the dr. for a tetanus shot? its been about 15 yrs

2 things: If there is no wound, not likely to have any infection. Otherwise you are indeed overdue for your tetanus booster that is supposed to be given every 10 years and that should protect you going forward for similar incidents.

Should be ok: Even if the nail had penetrated the skin you would be covered tetanus wise as they are good for up to 20 years. I would still advise making sure you get your tetanus boosters regularly (every 10 years is the recommendation fro the CDC so it's time for your booster either way).

Not rust: It is not the rust that causes tetanus, but clostridia in the dirt. You are due for a booster dose and should get one. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.