Tricky but something to consider :
A rivit setting tool is like a flat ended punch , a drift punch if you will , but the end is concave and by using it on the end of a dowel of wire , like that pin in your knife . . . the concave surface forms the head on the rivit .
If you were to find , or make , such a perfect size set then you could hold it against the end of that pin , tap the set with a steel hammer and form the sharpish edge of that pin so it would curl downward into the bone and be more like the shape that is on the underside / bottom of your image .
While forming the top of the pin the bottom of the pin needs to be suported . A flat strip of aluminum would do it .
Go very gradually . Give the set a tap and look at the result , Tap and look . Until the shape is nicely down against the bone and not gaping like it is now .
The down side is if you get over zelous and go too much too fast you could crack the bone .
Keep in mind this is how the pin was formed in place at the factory . You are just finishing the job they started .
You want to do the ULTIMATE JOB ON IT ?
Carefully grind the head of the pin off . Use a tiny drift punch the same size as the pin and press the pin out enough to "counter sink or counter bore " the top of the hole in the bone scale . (look those terms up)
Once you have your one counter sink , make a new pin , press this pin in and it will press out the old pin . . . but not all the way through yet . You need to counter sinc / counterbore the other handle scale .
Now press the new pin into place with it equadistant on both sides , a bit proud of the handle .
Use the rivit set to dome one end of the pin at a time until it is rounded over and down in the counter bore you have cut in each handle scale .
Now you have robust ends on the pin and the rim of the domed end is down in the handle scale rather than razor thin and weak from filing or buffing .
You might even want to get a crap knife from an "antique" or other used stuff shop and practice on it before doing your Boker .
I don't know how much interest (and patience ) you have . . .
But there it is .
