Even with the best materials and the greatest care, a wick can go crooked when a candle is made. It happens because the wax shrinks, often unpredictably, as it cools, pulling the wick out of true. When the wick gets pulled close to the glass, it can crack or break the glass and scorch or burn the label.
You can fix this while the candle is burning. Look down into the top of the candle and, if the wick is noticeably off-center, put it back toward the middle with a long, sturdy object like a knitting needle, long screwdriver, or butter knife.