My first thought is that your safety trumps silly "reserved" camping regulations. I have encountered this situation with brown bears. I simply continue a mile or so farther. In Yosemite you really do not want to camp in the known vacinity of bears. It is a sure be they will come around at night and disturb you. Even though I camp "bear safe" I am not one who can sleep well with a bear wandering around my tent and grunting. Each situation is different. Is the bear curious, hungry, territorial, or protecting young? MS is correct - you need to get educated from those who know.