I second what Pat said.
Those knots don’t look bad at all. Put some super glue in that one by the handle to stabilize it. Which I don’t think is even necessary for that one. You could scrape out any soft stuff, round the edges and I’d wager it would give you no problems at all. The other knot doesn’t look like any problem at all. Especially hickory. If the grain swirled around a knot that comes through the back, you’ll want to follow that swirl around the knot. If the knot comes out the side of the limb and it’s solid, you can act like it’s not even there.
Like Pat said with the super glue and sawdust. When you start layering and packing it will get hot and start to smoke. The deeper the hole and more you pack it the more smoke it’ll roll. I like to use contrasting materials in the holes. I’ll use horn, antler, blood wood, ebony. Essentially whatever I think will look neat.
Kyle