Is Itching Normal With Cast Boot After Injury To Ankle?

I stepped off an 8 drop off and have a grade three sprain. Two weeks after the injury I have episodic periods of severe itching where previously the tissue was severely eccymotic. The original injury had deep purple bruising half way to the knee, 3+ edema, numbness at the skin surface, and joint pain. The ankle has both lateral and medial injuries. I have been in a cast boot. After that background, I would like to know: is the itching expected and normal, when is it safe to walk on the ankle using the cast boot, and is there anything I should avoid to prevent worsening this.