You haven't mention that do you have any other related skin problems like Seborrhoeic dermatitis
or any history of any other kind of eczema in the past. If you have got associated Seborrhoeic eczema then it can not only affect the scalp
but other areas like face,sides of the nose,beard and moustache area and also the chest.
So may be the area is affected by it.it can also be a case of contact eczema
due to any allergen in the clothes,cosmetics,bedding or environment.
It can also be a Papular Urticaria
which due to an insect bite or crawling and leaving body fur or any other parts.
I would suggest to apply 1%Hydrocortisone cream
to the affected area twice a day,but there is no harm to let your doctor know about it because its worth having a look physically.
I hope this information would be of help to you.
All te best.