The incident Nasty referred to is probably exactly what happened to you, Az. In my case, it was a combination of fatigue, an extremely heavy khukuri, and some kind of weird superwood that Hollowdweller had found at the bottom of an abandoned uranium mine on a DoE reservation. (Okay, I made up that last part, but it was damned hard wood -- not much softer than Creosote-soaked timbers, actually.) The GRS took a bounce. I thought that a woodchip had struck me, or perhaps the flat of the blade, and there was a substantial (but painless) impact. Like you, I went on for a few more swings before a bystander (Roadrunner) pointed out that I might be injured, and like you, flexing the muscles -- well -- displayed them to me.

Fortunately the edge stopped on the bone and no serious harm was done.
(A little secret: I'm actually quite squeamish when it comes to the mysteries of the human interior. Barring illustrated diagrams, I have no interest in seeing what's under my skin and while the clockwork beneath is fascinating, I do not enjoying watching it work. Skin is cool.)
The wound was basically bloodless and did not hurt much, even after the initial shock wore off. It hurt quite a bit the next day. By the time I was back to work I didn't consider it worth showing to a corpsman. Some months afterwards I had it checked out due to a lump. The doc opined that it was probably scarring on either the bone or the tendon and to come back if it didn't go away by itself and was bothering me. It's over a year later now and the lump isn't going anywhere but it doesn't bother me and to be honest, it looks kind of cool. It also serves to remind me of what happens when I go off task.
In all seriousness, I should've lost that finger and part of the knuckle. We're still not quite sure why that didn't happen. Chalk it up to God's love for fools and a high calcium diet. I won't fault the edge on Nasty's khukuri.
If you've seen any of my later videos, you'll note that I keep my left hand up near my chest, palm in. I learned not to hold it out for balance after I hit it behind my back (another mystery) and I learned not to hold the work in Ohio with the GR. I keep it where I keep it now because I was tired of hitting it. This is a tough way to learn and an examination of my hands can tell many tales of woe and stupidity.
Watch the hands, watch the legs, watch the feet, watch the bystanders, and make sure that everything is in such a location that it won't be hit if the khukuri goes through, bounces off, turns, or gets thrown. Sooner or later all of these things will happen. I quoted a passage from
Bugles and a Tiger a while back where Masters talks about a Ghurka chopping his own thumb off while clearing brush, the point being that even skillful users sometimes have accidents. Look for ways to prevent them. Have a plan in place if something goes wrong. Do not forget that one moment of inattention can result in a truly life altering experience, and not for the better.
Since Kismet hasn't said it yet, now might be a good time to review the safety thread.