I masturbate with my left hand. One day, after using the wrong type of cleaner on a hardwood floor, I slipped while walking to the kitchen. I injured my left elbow, causing the area around it to swell up, and wasn't able to use that arm for a few weeks. One night, I tried masturbating with my right hand; it took a couple of hours or so, but I successfully finished. I trained myself and continuously got better with it.
I believe it is possible if you never give up.