If I like someone but my best friend is closer to that person and also like the person, should I still follow my heart?

You should follow the heart, that is your answer

I think if that person don't know you like her/him so you can ask her/him:"Do you like someone?"
If he/she say:"Yes" so you csn ask her/him 1 more question is:"So who do you like?"
If he/she say someone so I think you maybe give up. But if he/she doesn't answer your question, maybe he/she like YOU
By the way, just follow your heart.