1. Find out whether you are really in love
you might just have a temporary crush on him or her. indeed.
there are many reasons you might feel you are in love with your close friend.
for example:
you are on the rebound from another relationship and are looking for someone to cling to.
you friend got a new extra cute style.
you friend spend less time with you since he or she is dating someone else.
you and your friend are said to be "a love couple"
let some time pass by and see if your feeling change. if not. got to number 2.