When I was a student nurse, we were taught that the 'top number' could be classed as 'normal' if it was 100 + age, within the limits 100 - 145. The bottom number was classed as 'normal' if it fell between 60 and 90. So, assuming you are not younger than 41, your reading is within the normal range (if at the higher end). You don't say why you went to see the GP, but something as simple as a minor infection can make your BP go up temporarily.
The readings measure the pressure your blood exerts on your blood vessels when the heart is pumping (the top, bigger number - known correctly as the 'systolic' pressure), and when it is between beats (the lower number - diastolic). Things such as exercise, stress, dehydration, being too warm/too cold ... a bazillion different factors ... can have an effect on the systolic pressure for a short period. Doctors tend to be more concerned if your diastolic is persistantly (or dangerously) high, as this is the pressure when your heart is at rest.
Your doctor is not concerned about your BP - I know it's easy to say, but you don't need to be either. I have white-coat hypertension - my BP goes very high when I'm at the doctor's!! I have had a 24hr recording of it done twice to confirm, and unlike you, I HAVE been recommended to check it at home as I get reliable readings! But in your case, you will do more harm than good by worrying about it or self-checking. Try to relax and do some nice things to take your mind off it.