Yes being nervous can indeed cause an increase in blood pressure.
When you're nervous your heart begins beating faster and the faster your heart beats the higher your blood pressure is.
So if you're nervous and check your blood pressure your blood pressure reading will usually be higher than normal.
So it's important to stay relaxed and calm as well as being quiet when taking your blood pressure.
Once you've stopped being nervous then your blood pressure should return to normal levels
Normal blood pressure readings are usually 120 over 80 but even 135 over 85 can sometimes be normal and not be a cause for concern.
When your blood pressure reading gets above 135 over 85 then that is getting into hypertension and you should lower it or see a doctor to help get it lowered.