Thank you for your question. Although without being able to examine you I can not offer you the specific advice on diagnosis and treatment that you need, but I would try to provide you some relevant information about your health concern.
The localized skin irritation could be due the paresthesia after diabetic neuropathy. This neuropathy appears as a tingling sensation on skins and appears after long standing diabetes. Another possibility could be an ulcer formation in the skin of leg, called as diabetic ulcer. If you suffer continuous tingling sensation on skin of leg, please arrange an appointment with a neurologist right away who will evaluate the possibilities here and can provide you an appropriate treatment. Hope this information proves helpful to you.
Take Care & Regards!!!