Sorry for the bad news, but your only choice is to cover up or remove the burnt portion.
Covering up means paint, epoxy resin, or "scabbing" a piece of wood over the damaged, burned part. You can also inlet the stock for something decorative (engraved metal plate, large coins or medals, or two-dimensional animal figurines.
Assuming you want the natural beauty of wood, that means removing the burned-in part by sanding it off or scraping it off.
You can do this carefully and make the stock contours look natural. Try not to alter the shape of the stock.
HTH
John