That depends on how you really feel about your boyfriend. You must ask yourself if you are willing to leave your boyfriend for his friend who may not recipricate your feelings and then have them both not want anything to do with you. At the same time it is not fair to your boyfriend if you are having feelings for someone else - especially his friend. You are going to have to decide to suppress your feelings and stay with your boyfriend or leave him and risk what you have for what you may not have.
It is not unusual to feel the way you do for an instance but that is just that a brief feeling and usually goes away.