You stripped the screw head. Your going to need a replacement screw, so I would contact ride about that and see if they will do it. As far as getting the screws out goes. I don't have those bindings, but are the edges of the screw head exposed? If so, you could try to take a pair of pliers, the kind that lock, and lock them down on the edges, then try to turn the screw by gripping the outside. The only other way to take out a screw with a stripped screw head is to drill it out, but that's a little more involved and I wouldn't recommend you do it as you could damage the binding. If your not able to get it out yourself, I would take it to a shop and see if somebody can figure out a way to do it for you.