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Cortizone is an antiinflammatory medication and it does not decrease the pain.When injected it can cause side effect as Corticone flare which leads to more pain.
Apply ice packs regularly over the area where it is itching.It will help in itching and pain both.The symptoms should probably subside in a few days time.
If the symptoms worsen or you do not feel better after few days consider visiting the treating doctor for evaluation.
Take Care!