Probably nothing. Thing is, brakes don't really have a way to disengage. You pull the lever, it pushes on the brakes pads, you let go, it stops pushing. That's not the same as pulling the pads off the disc. After driving a few feet, they've worn to the point that it's almost 0 residual drag on the disc. But when you park it, stopping is obviously the last thing you do, so the pads are still in full contact. As long as the rubbing noise isn't audible when riding, and isn't rhythmic, you probably don't have a problem.
Once the weather is good, you can try riding to a slow speed, go to neutral, shut off the bike, listen while coasting, apply the brakes a little not to a stop, let off and listen. You should hear no rub when you first shut it off, and a little rub after you let off the brakes for a short time.