If there is any particles or dirt that made it's way inside the phone near the camera it can cause it to work improper or give a shadow on pics taken.
I recommend that you disassemble the phone carefully and use a can of compress air that you can pick up at walmart or online. Simple spray the compressed air and it will safely remove the particles that were bothering your camera.
***Important that you do not touch the camera circuit it can cause ESD and result in short circuiting the board.***
Use ESD strap or grounding equipment when working on.