cannot take the left over grommet out, cannot replace with new grommet, racquet not usable (cannot re-string....) the left-over grommet got stuck inside the whole, is there a way to take it out? thanks.
There is a dedicated tool that looks like an awl but has knurling on the tip which is designed for removing grommets. I don't have one so I use a small electronics philips screw driver where the diameter is just the right size to go through the holes (i.e. not too small). Works a treat. You just need to bend the flared flanges of the grommet back in and push/turn the screw driver gently and ease the gromment out gradually.
If worst comes to worst, you could take the handle off the racket and shake the grommet down out of the shaft. But this is worst-case.