Bubbacloud,
Let me add my welcome to you to the forum. Now, Reference your post and pictures . . . . OUCH!!!
After studying the pictures and seeing the size of your hands and the exact location of the "wound" my initial thought was exactly what Tracker posted above. That your thumb "rode-up" just enough, with out your being aware of it, and the slide just managed to graze that spot. Perhaps a few times.
However, if your certain that it's not the slide, I would suggest that when you go to range to use a bandaid to cover that vulerable spot BEFORE you shoot. That will give you some padding and protection right at that crutial spot without you're having to resort to a shooting glove. Congratulations on your new Pup. and again, welcome.
Regards, Quiet1