The holes (called a "port") allow air to move more freely when the speakers are playing sounds - the port allows for more efficiency, which can be important with small computer-style speakers. Do a Google search for Bass Reflex (the kind with a port) vs. Acoustic Suspension (non-ported)speaker types.
Unless the youngster jammed a foreign body in to the speaker as well, I doubt his finger would do any damage whatsoever.
Oh, and just to help out those who may not be native English speakers here on MacNN, and to make your posts far more readable, please don't use AOL-speak or cellphone text message abbreviations. It makes things harder to read, actually.