No problem Rich, it’s not the actual sensor you are cleaning just the low pass filter that sits in front of it.
Just be careful and use a sensible amount of force when wiping across with the swab.
Always worth checking after you have given it a puff out with the rocket blower, might have shifted it, but does sound like yours needs a wet clean
The original 5D seemed to be bit of a dust magnet, but the later mkII model seems much better, guess the sensor clean gadget does some good.
Only use a swab once and don’t try to wipe it back the other way, just drags any crud back across