Halobetasol propionate ointment lightened my skin on my cheek around where I have psoriasis. How could I fix it?

See a dermatologist. Avoid use of steroid on the face, especially such a potent one. Psoriasis on the face is sometimes in the eyebrows, very unusual on the cheek. You need careful evaluation by a professional who is knowledgable and experienced with psoriasis as well as other skin disorders. See a dermatologist.