HI Mamasan,
yes, stress can increase your blood sugar levels. Did they tell you what the levels were at the first fasting BG test? If it was much less than 6.2 (e.g. 5.5) then that would be still in the normal range. I believe 5.7 is where prediabetes begins, and 7 is for type 2 diabetes.
HOWEVER, and this is very important for you to understand. One reading of fasting blood sugar is not enough to diagnose either prediabetes or type 2. You will need an HBA1c test, which measures the AVERAGE of your blood sugar over the last 2 months or so. That is much clearer for a better diagnosis.
Even if you are found to be prediabetic, there is much you can do to hold diabetes at bay. My advice is to read, and read, and read all the good advice in this forum. There is much you can learn here.
I am prediabetic and having cut out refined and starchy carbohydrates (bread, pasta, rice, potatoes, sweet and sugary things) I have brought down my own blood sugar levels from an average of 6.22 to 5.2. I measure my fasting blood every morning and then take the monthly average.
Even then, it can vary widely. I have pricked my finger (for some blood) and got a reading of 6.1 once, thought it was a big high, and immediately took blood from another finger and got a reading of 4.8.... The reason I tell you this is to show that one reading alone is not enough.
Good luck. Let us know what the doctor said and what the results of the HBA1c test will be. And keep reading the forum.