Wearing a necklace given by your ex may have an impact on your current boyfriend, because he will think that you are still missing your past relationship, which will make him feel uncomfortable and jealous. In order to avoid this situation, you can try to understand his feelings and take positive actions to deal with this problem. You can talk frankly with your boyfriend and explain what this necklace means to you and what you are going to do with it. Or, you can consider putting away the necklace and not wearing it in front of your current boyfriend to avoid unnecessary contradictions and misunderstandings. The most important thing is to respect each other's feelings and strive to establish a relationship of mutual trust and respect.