Please help - I'm attracted to my fiancee's best friend?

Basically I've met this guy for the first time when my fiancee and I went out for drinks and a meal with him. My fiancee is always telling me how he asks about me all the time and at first I didn't think about it . Then at my fiancee's party - we were left alone to talk and we talked and talked all night ( while drinking) and he (the friend) began examining my necklace . There was a tension and I quickly moved away from him. But I can't get him out of my head - I love my fiancee alot and I would never cheat but I'm so attracted . Please help