Looks pretty good for a first attempt if you ask me.

As far as filling the hole, I'd just mix a paste out of some of your briar sanding dust and waterproof Titebond wood glue, then pack it in the hole. Since you're rusticating and staining dark I don't think you'd even notice it. You'll probably have to take an Exacto knife or something to V out the flaw back to solid wood and to make room for the paste. I'm sure this isn't the 'Official' method but it's what I'd do