What kind of lotion or ointment can I get for my heat rash underneath my breast?

I just noticed it today underneath my left breast that I have an heat rash. I never had this before that I'm aware of,and I don't wear a bra during the day when I'm at home unless I'm going somewhere.

I use dove sensitive soap for sensitive skin. I don't know if that could had caused my heat rash underneath my left breast or not.

I'm sure whatever I have may not be alarming and may go away with lotion or something.

The things that women has to going through that we all hate!!!