Hi, Welcome to HCM.
Rash over stomach & chest means you are having it over covered parts. It may be due to many things. Folliculitis
is common in covered areas.
Beside that contact dermatitis
due to contact with clothes,chemicals may be the cause. Psoriasis
, drug rash also can occur at that part.
But dont worry, effective treatment is there. You can apply calamine lotion twice daily for 10 days. Hope it will help, if not then please consult a dermatologist
. He can identify the lesion after examining it.