How to delete synced photos if original folder is deleted from pc?

So I synced a bunch of photos from my PC to my iPhone 5S and deleted the folder after. I put those photos in a safe lock app, beause they are private, but i couldn't delete them from my photo library after. I know i need to re-connect to the iTunes and unsync that folder but like I said, I already deleted those photos. As a matter of fact, these photos are only found on my iPhone now. Please if anyone knows a way to delete those photos without having to resort to completely restoring the phone, i would apprecite it. thanks!