I'd guess it'd depend on the level of discomfort. Generally speaking discomfort indicates that your energy is not flowing the way it should or that you ommited or improperly did some part of the projection excersice. I'd suggest you check your breathing. Breathing deeply for too long, especially if you breathe fast, can increase the level of oxygen in your blood and that can result in tingling sensations and stiffness in the extremities.
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