i am a pharmacist and also run a bit. in my first every race i suffered with bleeding nipples. they were very sore for days afterwards. there is a product that is only usually supplied on prescription, but you can buy it in pharmacies by asking the pharmacist. the product is called TEGADERM. it is like a sticky piece of cling film you can cut it to size and stick on you nipples. it pretty cheap & stays on for days after. i have just run my first marathon, dublin (4h 19min) and the tegaderm worked a treat.