I dont think the sound quality should be affected. If that is the case, put the fabric grills back on and forget about it. if you are bothered by the thought of the dented dust cap (as you would be probably if you knew about a stuck bright pixel on an LCD screen), then supposedly, you can take some tape and try to pull it out that way. Be careful though, a dented woofer should be OK acoustically, but a woofer with a hole would be disastrous!