I never apologize in that kind of situation, nor do I understand why anyone would feel the need to.
If you hit the net cord on purpose, then I can see why you should apologize for it.
But I don't know of anyone who can do that intentionally.
It usually just happens, the ball can end up on either side, it's just luck, so what is there to apologize for???
Wilson BLX ProStaff 90: 368g, 7pHL, SW=352. (Wilson NXT 49lb / Lux AluPower 45lb).