how to check if iPhone has been opened without going to iStore

I recently bought a used iPhone 5s in golden.The dealer told me that the phone has not been opened or repaired but I doubt it.I was sitting when I turned on the phones flash and I noticed the flash peeking out of the lock button and below the gap where the glass screen molds with the golden sides on the front also there is a minor white light coming from the bottom of the screen. is it opened? there is no apple store around where I live and i am pretty depressed so please HELP ME