There isn't sufficient information to reach a specific diagnosis as the skin lesion would need to be seen. I would advise you to meet a dermatologist so that you can be examined and undergo the necessary investigations to find the underlying cause of the problem and have it treated accordingly. For the time being you can apply a lactocalamine lotion to the lesion but I would advise you to follow up with a dermatologist.
Next Steps
Follow the steps as advised
Health Tips
If condition persists or worsens visit the dermatologist at the earliest