I've been in several accidents on my bike, and it sucks. Hope you heal up quickly.
When asked about helmets, I usually just tell them that I was wearing my helmet. And that 16 oz of styrofoam doesn't do a heck of a lot against a ton of metal bearing down on me. There's a tendency in North America to blame cyclists (every police officer involved in a car/bike crash that I've ever run into will absolutely be looking to blame the cyclist), so if you run down the checklist (helmet, reflectors, lights, high vis clothing, reflective clothing, etc.) of stuff a safety conscious person does then that tends to shut them up.
Sure, you can go deep into a discussion of how bike helmets aren't actually designed for crashes with cars or a bike at speed (the way they're tested really is only to protect against falling sideways off your bike and maybe hitting a curb at worst). Or how cyclists with helmets get cars passing them closer than cyclists without helmets, which might actually make their net riding more dangerous. Or strategies for where/how to ride. Or talk about the studies that show helmet laws actually reduce cycling . . . and when there are fewer cyclists on the road it becomes much more likely that a motorist will kill you simply because they're unused to driving around someone on a bike. But they don't actually care about that, they're just looking to appoint blame - so I've found it's rare that we need to dig into that. You're not the fat guy in a metal box of death spewing out pollution, so you're the weird one. :P
FWIW, I actually stopped riding my bike on the sidewalk because it's was causing more accidents with cars for me than riding in the road. Counterintuitive I know . . . but cyclists move faster than pedestrians, and cars don't look far up the sidewalk when they're turning into a driveway, entrance to parking lot, whatever. If I'm on the sidewalk now, I tend to dismount because it's just too easy to glide along a little too fast when you're in the saddle. And all that said, I also realize that every cycling situation is different. There are of course some places where it makes sense to ride on the sidewalk - I just find there are far fewer than I had initially thought.