IMO, pick out any black manky stuff with a needle file ground to a fine chisel point (or similar tool). If the knok can be waggled like a loose tooth take it out, trying to leave the parent wood sound. E.G better to push it out than drill it.
Clean away any manky stuff as it will just collapse and cause a pinch.
Fill with a wooden peg from the same yew if possible or yew dust epoxy mix or CA and dust if you prefer.
If the knot has jus tabout fallen off the edge of the bow, it may be best to just leave it, and avoid disturbing the grain.
Soooo.
Top pic, looks fairly clean, I'd flood with low viscosty CA, probably leave it...
Bottom pic, I'd pick at the black stuff and see if the knot loosens... if it comes out, plug, if it doesn't pack round the gap where the black stuff has come out with dust/epoxy mix
Del
