Exercise affects blood Glucose in ways that can be difficult to predict in the short term. Vigorous exercise can often raise BG in the short term as your liver dumps glucose into the bloodstream to keep up with the energy you are using, just like it does every morning for those who have noticeable Dawn Phenomenon (both in diabetics and non-diabetics). It may be that your liver over-compensated, which should become less of a problem as you become fat adapted (assuming that you are low carbing).
Muscle building exercise (with weights for example) tend to be best for lowering BG in both short term and longer term since it is non-aerobic, using less energy plus extra muscle means extra storage for glucose outside of the bloodstream.