Remove the case and/or screen protector that is interferring with the proximity sensor on the device, the screen should be turning off when near your face.
Zoot Zoom wrote:
If I reset the phone will I lose all the pictures etc as well as anything stored locally?
Only if you are completely unintelligent.
A reset does NOT remove data. Only a restore as new will wipe data from the device.
Then again, any intelligent human being would not be relying on a device so easily lost/stolen or damaged as sole storage of important data.