The hole is less than an inch in diameter and has gone through the carpet and the underlying flooring so that there is now an 8cm gap between the hole and the ceiling of the floor below. Is the infrastructure of the whole floor likely to have been compromised? Please help!
No problems with the floor infrastructure...you don't say how this occurred but the floor boards are laid on top of timber joists and normally you'd cut the damaged board away with a jigsaw before fixing in a new panel. However, if the hole is round, why not plug it with some dowel which you've sanded to a slight taper, add some glue and hammer it in? When dry you can cut the excess off and then plane it down to floor level.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix general d.i.y.