Hello & welcome,
First i need to know that have you taken complete course of Antibiotics after extraction of your tooth last month ?
This is because, diabetics are somewhat more prone to any infection including the involvement of the nerve
as compared to other patients.
Even you had abscess
in your tooth which requires special care especially by the patient. Maintaining cleanliness to optimum is of utmost importance for you.
Get you blood sugar level checked.
Visit your dentist
who extracted the tooth immediately to get clinically examined to know any other underlying causative factor.
or itch sensation might indicate the nerve involvement either by infection which has spreaded there or due to injury
to nerve while extraction due to close proximity to tooth structure.