This is a new symptom for you so it's best to go and be seen and get it checked out since it's been there for a week. do not shave again until you've had this looked at and find out what is going on.
grace
From what I understand a herpes blister would not be there that that long while not popping. I've learned from this board that then you get a blister they pop quickly, are filled with clear fluid, and are very painful. If and/or when the blister pops, go see doctor within 48 hours for them to get a swab culture! Or you can get a blood test (igg test) for anti-bodies! Hope this helps!