I thankfully havent had any sword mishaps that involved blood loss or scars.
Ive been nibbled on by a couple of sharp swords. Mere scratches.
One was bad hand placement on the scabbard of a katana so the edge grazed my skin as i resheathed it. The other was from a wakizashi. When I was resheathing it my body thought it was a katana so when I extended my arm all the way out the tip went sailing past my finger and left a decent scratch. The training sword I use in class has yet to leave a mark on me. I plan on keeping it that way too

. I have dinged the tip on the floor once when we were doing angle cut drills in pakosae. <--- that stance is a fun one.
I think my furniture in the apt has suffered more damage than I. There are various scrapes and scratches on the furniture in the room I practice in. It was more from when I first started when you are still learning about spacing and such.
I have read of 3 serious dandies of sword mishaps on various other sword forums.
1. Man self educating in iaido from a book. He is practicing with shinken and decides to do a fancy noto, misses, and runs the sword through his whole forearm. It entered in the inner wrist area and a couple inches of the tip were sticking out the other side just in front of his elbow.
2. Man is doing cutting exercises outside and the sword he was using was poorly maintained. He wasnt doing very well and another man was trying to help him. He wouldnt accept and kept getting angrier and angrier, swinging harder and harder. In the middle of a swing the mekugi /peg failed and the blade flew out and straight into the chest of the other man. <-- he actually lived.
3. Man is doing cutting exercises and his follow through on one of the cuts went too far. So far it cut right through his calf. He managed to crawl to the street and he was lucky that a couple nurses were walking nearby.
4. Man actually in an iaido class is doing an advanced kata. (i cant remember the details if the sword was sharp or not) But the move that got him was a thrusting/stabbing move that is directed to an enemy behind him. He misjudged the angle and ran himself through the abdomen.
Ow....
My stomach was churning a bit describing these as I remember the pictures that were posted. I can find the links to the postings of these if anyone wants.
Just goes to show how focused you have to be when training with weapons