Athletes tend to overuse ice due to its numbing effect, but it can improve circulation if used wisely. I prefer alternating it with heat in non-acute stages of an injury to keep immune activity and beneficial inflammation active.
If you must run this race (I wish you would reschedule), have your peroneal (fibularis) muscles and rear-calf plantarflexors trigger-pointed before the race. It will hurt, but probably less than running without. Tension in these muscles puts unrelenting pressure on the tendon sheath below the malleolus, but produces the same pain even when actual tendonitis is not present. The symptoms are very similar, and you have noticed it flares up during/after use, rather than all the time.
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