Not enough time to do anything about it, but then it was only a meter or so wide. At that side it was probable to be harmless. Ten times bigger, though, it starts to get worrisome. A hundred time the diameter, you need to stand up, take notice and consider launching the nukes.
This was not the first impactor to be detected prior to impact. In March, a 2-meter asteroid was detected 2 hours prior to impact.