You will have to set the iPhone back up as a new phone so hopefully, you am a backup.
1) hold the power button for 10 seconds or so
2) while continuing to hold the power button press and hold the home button. Hold both buttons together for 5-10 seconds
3) release the power button but continue to hold the home button
4) while holding the home button, plug the iPhone into your computer using the charging cable
5) keep holing the home until iTunes recognizes the iPhone
6) iTunes should ask you to restore the device