What Causes Itching Inside Vaginal Canal?

I have itching inside my vaginal canal, no pain when peeing no itching anywhere else just one area, its almost painful. I am 22 years old, 5'5, 160 lbs. I smoke 1/3 of a pack a day and I am in a long term relationship. I had some pain when urinating about a week ago but it has since stopped and the only discomfort I feel is this