I had the same problem nearly in the same place on the comb. The bug hole was a bit more forward than yours and it kept getting bigger as I worked the comb down to the final profile. I took a scrap piece of material that I had cut off the stock blank and cut a piece slightly larger than the area I was trying to repair. I oriented the repair piece so that the grain would match the direction in the hole. I tapered the repair plug and inlet it into the cavity as close as I could get to the edges. I took the plug out and stained the mating surfaces of the plug and the stock. Next, I used liquid Acraglas from Brownell's (with stain added to best match the stained wood) to flood the cavity and mating surfaces. Then, I put the repair plug in the opening. The trick was to get a good fit between the plug and opening, and it was critical that the final shape of the comb was almost there. I worked the plug down to match the comb profile, and applied stain and finish. The repair was invisible, but it took a bit of work and time. I sent photo's to the customer showing him the damaged area before and after the repair to see if he was OK with what I had done. He took the rifle and has had it for five years now without any issues. If I can find the photo's I will attach them to this message. This has happened to me twice since 1978. The first time I scrapped the stock and started from the beginning with a new blank. Bummer!!
Good luck.
Roger Sells