Q: I accidentally synced all my photos from my computer to my phone, and now I have no storage.  How do I delete these photos, without deleting all my photos?

There is no need to worry. your photos on your computer is not gonna go anywhere, follow these steps

• Connect your phone to itunes
• Click on your device
• In the left there will be a folder "photos", click on it
• Now de-select the folder and press apply.
• Only photos on the phone will be removed,no photos will be lost from your computer

See the instructions below from Sync photos from your computer to your iOS device using iTunes - Apple Support

Delete synced photos

1. In iTunes, locate and click on your device.
2. Click Photos.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.