Acne vulgaris is physiological response to your hormones(androgens) after puberty.
It can happen where the sebaceous glands are distrubuted like face & neck, front and back of the chest.
There are different grades of acne , where 3 & 4 are severe form where it leads to complications like post acne scarring & pigmentation.
Stress,lack of sleep, menstrual cycles & irregularities , genetically it can aggravate or flare up the acne lesions.
So it need to be maintained not one time treatment.
As I told depending on the grade we can treat.
Like topical &systemic antiboiotics,topical &systemic retinoids(isotretinoin), topical keratolytics combination with antibiotics.good face wash -1% salicylic face wash.
Chemical peels(salicylic ,mandelic..etc) ,lights therapy.. etc will help to control the acne and prevent the complications.
Next Steps
Consult near by dermatologist for further treament & evaluation.