Transparent vertical shadow box on left of screen

I recently purchased a mac book pro 2019 that was refurbished. On the left of the screen there seems to be a transparent vertical shadow box that only appears on white screens. It flashes and gradually turns pink when there is no movement from my mouse. The only way it goes away is if I move my mouse constantly. If I am watching a Youtube video or on my home screen this shadow does not appear. Please help :( I literally just purchased and not sure if I have to take it into apple.