Yes it does have an effect. However it would take a 2007 pixel peeper champion of the year to care or notice... probably not even notice.
Best thing to do is set up a light on a stand, turn on the modeling light, turn off the lights in the room and notice the light you get on the ceiling from the hole. Its certainly going thru there. Then just take a few images, maybe even meter them too. One with the hole open and one with some foil over it.
Can you tell a difference in the shots? Do they meter differently?
I would bet probably not. But if you are that guy, just cover it with gaffers tape or something.