Welcome to HCM.
Wounds in genital area often heal late due to the moisture and hygiene issues.it might even take 4 weeks to heal.Since you are diabetic it takes a bit longer.
As your sugar levels are normal so need not worry.
As far as usage of Ceftum
500mg is concerned, you haven't mentioned whether you have any fever
especially at nights and you did not even mention how you got injured( sexual or non sexual). If the wound is due to sexual contact it could be an STD
or could just be due to friction injury( diabetics are prone for such injuries).
In case if there is any pus coming from the wound you can take ceftum500.
If not applying simple antibacterial creams like soframycin
or cipladine should be enough.
As you have mentioned that it is healing but slowly, i dont think you require any oral antibiotic.
Applying MEGAHEAL ointment will definitely heal it quicker.
My suggestion would be apply Cipladine or soframycin in the morning and MEGAHEAL ointment at nights. This should solve your problem.
Wish you a speedy recovery.
Dr Sai rajesh