Ok, what you'll need to do is to reset the iPhone and restore from that backup.
You should be able to restore from iCloud by restoring the device. It's important to note that this will erase the device so if there is anything on there which you currently wish to keep, let me know. Assuming the backup is still in iCloud, you should be able to do the following to return to the last backup:
then tap “Erase all content and settings”
When the device restarts, it will display the Setup Assistant. In the Setup Assistant, sign in to iCloud, tap “Restore from a Backup,” then choose from a list of your backups in iCloud.
Your device is restored as follows: Your settings and accounts are restored from the iCloud backup you chose. Your device restarts and begins downloading your purchased music, movies, TV shows, apps, books, Camera Roll, and other content.
You may be asked to enter passwords for iTunes, App Store, and iBookstore accounts to restore purchased items. If your device can’t download the version of an app that was backed up, it downloads the latest version.
Progress bars appear below Home screen icons for apps being downloaded. To make an app a priority for downloading, tap its icon.
To check if the information on your device is fully restored, go to Settings > iCloud > Backup.
If the photos were backed up properly then they should restore just as you had them.