Long term it probably will like the extra sun it is getting, assuming you do not live in a hot desert...
Behind glass the sun should not go beyond stressing the cactus (ie. there is very little risk of actual sunburn occurring), but you may want to see if your current watering regimen is in tune with the new lighting conditions. Ie. the new lighting conditions may cause your pot to dry out faster because it is a lot warming in the window sill compared to where it was before.
Just be careful if you increase your watering frequency to make sure the pot still pretty much dries out before watering again.
