If you have a third party claim on a video because of the audio, you may be able to fix it by either swapping the audio on your video or by removing it altogether.
To resolve your third party claim by doing an Audioswap click here.
You can change the audio on your videos if you are unsure if it is okay to monetize your existing audio. Please take a look at this page for instruction on how to do an audio-swap on your video.
Songs that are from the YouTube free Audio Library, you may use them in videos that you monetize on YouTube. However, some of these songs are ad-supported, indicated by this icon 
As a partner, you have access to more than 25,000 songs on Epidemic Sound! Check out this link for more information
Please note that there may be some limitations on removing the audio depending on the video's view counts so sometimes it is not possible to remove or replace your audio on a video that has a third party match.