Rapid change in bp what could it be?

BP Flucctuates norma: It is normal for BP to go up and down by 10-20 mm related to physical activity and emotional states. So you have to be calm and rested for 10-15 minutes before your BP would stabilize and that is the correct value. Get a baseline value by checking on 3 different days and then use the average value as your real BP for future reference.