there is a video I have on my youtube channel when I was in a fort, and I knee'd down on a rusted old drywall screw sticking straight up. I barely pricked my skin, but if I wasn't wearing knee pads combined with good padded pants, I'd be in serious trouble right now.
That is terrible that this happened to you. I really hope you have a fast recovery and definitely invest in some good knee pads when you get back on the playing field.
My personal recommendation is the Dye Knee Pads, they've saved me more times than I've ever thanked them for. Sprinkler heads, leftover stakes in the ground, rocks, roots, glass, puncture items like twigs and screws
That hurts just looking at your injury, I hope you feel better soon :-(