If you believe the strike is invalid, here are a few ways to resolve a copyright strike–wait for it to expire, get a retraction, or submit a counter notification. Note that deleting a video with a strike won’t resolve the strike. More details here: https://goo.gl/YkBvnN
If you feel the claim was made in error or if you have all the rights to use that copyright-protected content, you can always dispute the Content ID claim by following these steps: https://goo.gl/fHCa7u . Hope this helps.