Depends on how handy you are, what kind of tools you have, and your tolerance for a possible slip up.
Wear safety glasses.
You can get it done by taping the knot up to protect it from dust. Then secure the handle in a vice. Or onto a lathe. Use a little hacksaw or rotary tool. Go slow. Take care about staying away from the knot and work your way through it. Don't rush.
If you use a power tool you should consider a good dust mask to protect your lungs.
Or wrap up the thing in an old rag and crack it with a hammer good and hard. I did that once but don't recommend it unless you are willing to accept possibly breaking the knot also. It's brute force but is less time consuming.