While putting back a tire without appropriate tools (screwdriver...), I made a dent in the wheel (aluminum, I think). Is this bad ? Do I risk more than a puncture driving with this ? It looks like this:
Hard to provide an answer based on a picture but I would not commute to work on a wheel like that. If I had a light trail by my house I'd risk a slow ride or two to see how things hold up. But I'd be looking for a replacement wheel (not so easy now that COVID has messed up everyone's supply chains). Also check that the wheel wasn't bent out of true (center).
I'd wager your brakes don't work quite right when they clamp down on that dent. Over time the dent would likely accumulate grime from the road and from your break pads. Then you're in for uneven brake wear on one brake track and pad. So long term I don't think you can count on using that wheel.