Open TikTok and go to your profile
Tap the menu icon
Open Settings and privacy
Go to Activity Center or your activity history, if available
Find your reposted videos
Open each reposted video
Tap the Share button
Tap Remove repost or Undo repost
Repeat for each reposted video
If no bulk option appears, delete reposts one by one
If the repost option is not available in your version, update TikTok and check again