Boyfriend's best friend have a crush on me,what should i do?

On my birthday party, i received a lot of presents,but one of the present make me worried and upset.It is a ring with a note in the case said:Give me a chance to love you. On the other side was a name Jack.If just a common friend,i will give a smile only,Jack is the best friend of my boyfriend,he care about him very much.I do love my boyfriend very much,but i don't want to be the person who break their friendship.I hope they can continue their relationship forever.But i must give back the present to Jackand refuse him,i don't know what i should say,so i avoid to meet Jack,but Jack call me every night.When my boyfriend ask what present Jack give,i lied to him .Oh,God,please give me some suggestions .Looking forward for your reply.