It honestly does not make that much of a difference when you weigh yourself in general. The main guideline for weighing yourself is to just do it at the same time each day, or week.
The body's weight fluctuates constantly, and after a workout, you may appear to weigh less, especially if you have lost any significant amount of water through sweat.
Additionally, we tend to weigh less in the morning than the evening. In the morning our food is digested and stomach is generally empty. In the evening, you appear to weigh more because of the extra food and water added to your body during the day.
So, just weigh yourself at the same time every day or week for the most accurate measurements.