Confession

So i don't know what to do. My boyfriend's best friend has recently confess to me that his in love with me. He makes me feel uncomfortable everytime we (my bf and i ) around him. One day he even threw a pass at me. I don't know what to do. I really do love my bf. Should i tell him what his best friend feels for me or should i just keep it to myself? What if he doesn't believe me? I don't want to loose him. I also don't want their friendship to end because of me. Any advice ladies?