iphone 6s camera problem

I just bought today a brand new iphone 6s, on white color, but it seems that the camera is having some issues. I just discovered that if I want to take a picture with the main camera, there is some black spot that won’t go away. at first, I thought that the glass of the camera might be dirty, but I cleaned it and the spot won’t go away, so it’s on the inside of the camera. Any suggestion of solutions? Thank you very much!