Looks like a bubble in the resin to me.
If you want to save it, you could possibly put some sanding dust or swarf off the blank into the hole and fill with CA, you will be able to notice the repair though, may be able to hide it with the clip. Or you could try and make a feature out of it and fill with something that really contrasts with the blank, brass filings, or get an offcut from a blank with different colours and smash it into little chips, fill the hole with that and CA. Plenty of options.