iCloud: Delete photos from My Photo Stream in iCloud
When you delete photos from My Photo Stream, they are removed from:
The My Photo Stream album on your iOS device (iOS 8 or later) when iCloud Photos is not turned on
Your photo library on your iOS device (iOS 8 or later) when iCloud Photos is turned on
The My Photo Stream album on Mac and Windows computers, and Apple TV
Note: In some cases, My Photo Stream is not available for newly created accounts. See Keep photos up to date across devices with iCloud.