TB skin test positive?

I had a tb skin test done a few days ago and the nurse read it today saying that it was positive and I need to see my doctor. The red bump is almost gone. I also had chest x-rays done the same day as the tb test but the results of the x-ray is normal and clear. I don't believe I have been in contact with anyone that has tb though and I did test negative on a skin test when in high school. I do remember getting a booster shot for something when I was a kid. It was a 5 or 6 hole injection or tester? maybe for tb. This is the first time I tested positive. Could it be a false positive? I also had the hep A vaccine done in the same arm as the tb skin test at the same time, would that create a false positive?