BillR writes, “Don’t know what “shinny” is”:
Having grown up in southern Ontario, I knew it was a game sorta like hockey, so this is just a cheap pun. Wikipedia adds more detail, of course: https://en.wikipedia.org/wiki/Shinny
…which is interesting, because I played a lot of street hockey and never once heard it called “shinny”. Nor was raising the ball (never a puck!) forbidden, nor were teams chosen by throwing sticks into a pile. May be a regional thing. Body checking was indeed not part of the game, though of course it happened occasionally.
We’d get out there of a winter’s Saturday morning–the churchyard behind my parents’ house was ideal, except for all those cars on Sundays–and play until it got dark around 4, skipping lunch. Nothing quite like taking a frozen tennis ball to the ear after you’ve been outside in subzero temperatures for several hours: first you feel nothing, then it starts to itch, then burn.
Good times!
Comics I Don't Understand 
My guess is “shinny” refers to his shin injuries, but I guess without knowing what the game is called the joke crumbles.
I had assumed it was a reference to the english martial art:
https://en.wikipedia.org/wiki/Shin-kicking
I found this excellent description: “Shinny is to amateur ice hockey what wiffle ball is to baseball: anyone can play, anywhere, with no special skills required. Simply swing a stick at an object on the ground, and you’re pretty much playing shinny.” Also, the name shinny itself probably comes from “shinty,” a Scottish game similar to field hockey.
I follow a YouTube channel, The Hockey Guy. He lives in Abbotsford BC. Occasionally he has a meetup at a local park, where they play “ball hockey”, which is pretty much as Boise Ed mentions. No slapshots allowed. His wife serves as timekeeper and scorekeeper, while doing a live stream for the channel.