It just goes to show that even when you think that you have taken every precaution with powered machinery there is something that can go wrong.
I learnt the hard way 2 years ago that when using an angle grinder you must make sure that what you are cutting cannot move in any way. The concrete slab I was cutting was fine until the monent that I cut through it and the two halves parted company. One pivoted and momentarily trapped the cutting disk, jerking it upwards and throwing me off balance. The cutting disk, still with the power full on, came down on my left hand cutting into the side of my thumb, not quite reaching the bone and luckily missing the tendon. I had to have a nerve micro-surgeried and this now gives reduced sensation, but basically I'm back to normal.
I did have an irritation along the wound for abut a year then one day noticed a small dark blue dot under the skin. After careful investigation, thinking that I had got some sort of splinter in there, it turned out to be the end of a stitch that had not been removed. A bit of a tug on the freed end and a knot appeared, so I cut through below it and removed it myself. No more itch and the wound has looked a lot healthier since!
So, be careful with machinery and how you use it and make sure that you get the correct treatment if something happens.
Robin