Blood Pressure is very much fluctuating entity, within few it can change abruptly. So if no underlying cause, then it should be normal within few hours after severe stress
may persist up to very long time after the stress and it affect blood pressure. So your main concern should be to remain anxiety free when the stress is over. If required you may take some anxiolytic for a few days.
However as your BP is too high I feel to exclude any other medical cause. Then you have to try some anti hypertensive. Keep record of your BP 3-4 times daily specially when you are relatively stress free.
MECHANISM:in stressful situation
anxiety----> Several metabolic and physiological changes-------> Increase O2 demand ------> More blood needed----->More active heart--->high BP
Hope you got it.
Best of luck.