Thanks for posting your query.
Do you have some blisters at affected skin site?
Do you have any difficulty in breathing/ fever?
There may be following possibilities: skin disorder/ nipple or breast pathology/ muscular or deep pathology.
Skin disease may be herpes zoster
, a viral disease , self remitting and at times very painful.
Breast pathology may be mastitis
or malignant changes.
Muscular pathology may be painful myalgia
Deep pathology may be bony in origin or lung pathology.
As per superficial nature of illness, there is less possibility of lung disease.
You should consult with physician and dermatologist
and should go for chest x ray and mammography
These 2 investigations will clarify your disease.
Dr. Mayank Bhargava