Lately my nipples have been dry,and somewhat sore, my periods not due for about 10 ten days, my partner and i have protected sex,what could this be?

Just to be sure: Just to be certain, I would check a pregnancy test as if it is both nipples/breasts. If not pregnant, an irritation from clothing (like an allergy) or a mild infection could cause this, try some vaseline and if no help in a few days, see MD.

Irritation: Likely this is caused by dry skin irritation. Try getting some lanolin (usually found in the breastfeeding section) and apply a small amount to the nipple and areola after you shower daily. See if it does not improve in a week.