What causes ulcers on head?
infestation? needs examination
I went through the query and understood your concern.
The features you are referring to the lesion does not look like fungal infection. It suggests more towards infestation. Even with staphylococcal bacterial infection there will be localised infection that spreads locally along with ulcer and pus formation. So I advice you to get the lesions observed under simple microscope by an dermatologist just to diagnose whether its an infestation or infection.
In untreated diabetic the chance of pyoderma and repeated infection is more. So just to rule out get checked for your blood sugar and complete blood count. This will help in diagnosis.
So in summary the cause may be most probably infestation. Needs further examination for diagnosis. Topical creams are available based on type of infestation. So based on the diagnosis we can treat which will completely cure your problem.
I hope this information helps you. Feel free to ask for any further queries. I will be glad to answer them.
Wish you good health.