I wouldn't worry about it at all. It's a known issue on almost EVERY HTC phone to date. The Hero had its screen that collected dust under it, then the Incredible had light from the bottom, along with the Evo 4g. The evo 3d has the search key that has half of it lit from the backlight on the screen at all times when the screen is active.
Light leaks are possibly the only hardware flaw HTC consistently makes, along with screen separation problems over time.