Step 6: Fixing the knot
With paracord, there is a geniune issue with the core; it'll look horrible if you just cut the cord, so you'll want to either melt it or tie a tight knot around the end with a thinner rope. The latter method is far outside the scope of this instructable, so I'll just recommend you use a lighter (or like I did - a gas stove) and melt the end of the cord.
Subsequently, sew the ends together with the surrounding knot so that it can't slip. I just used black cotton thread and an ordinary sharp sewing needle for this.
And then, finally, to make sure that these melted blobs aren't visible while you wear the ornament. Again, I use black cotton thread and a sewing needle to just sew the very ends together underneath a well-hidden part of the knot.