After reading your history it appears that your might have developed Impetigo over forehead area which is the bacterial infection of the skin. I advise you to take care that your son is not pinching or scartching the area. You can apply an antibiotic cream such as gentamycin
cream. Antibiotic tablets
are must such as Azithromycin
under medical advise. If itching is present then can take benadryl accordingly. Consult a dermatologist
to look for the exact situation and treatment of the problem.