You can also plug the holes with epoxy mixed with balsa dust (mix the epoxy well before adding the dust). Put masking tape over the lower opening and fill from the top. This is a very strong filler. But don't use this method if the hole is open to a cavity within the wing. it will take too much epoxy and weigh too much.

It might be easier to plug the mounting block(s) in the fuselage and re-drill them. It's also a much less noticable fix if the holes in the wing are suitably square now. Easier to align the new holes, too, as the wing holes are the guide.