I Have Developed Chest Acne, About A Year Ago I

I have developed chest acne, about a year ago i had like a cyst right in the middle of my chest never thought anyhing about it i would just cover it up with make up, about three weeks ago i broke out like crazy right above that cyst it is very painful and irritating. My family doctor prescribed me clindamycin .1% and tretinoin cream .1%. I havent seen any results so far what should i do?