Thanks for the query,
the waist line is prone to irritation due to constant rub with clothes.
It might be an allergy
due to cloth or dye.
Internal organ problems cannot present with just burning of skin.
Please meet a dermatologist
for final diagnosis and treatment
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.