Hi..thanks for your query.
The lesion you mention can be most commonly either due to Psoriasis
.But it is unwise to start on any therapy without the correct diagnosis.Both these disorders might need short term /long term therapies ,with remissions and exacerbations.
For now , you can start with an oral anti histaminic daily , this prevents you to scratch the lesion .Continue using medicated moisturizers .
Hope this helps.Take care!