The photos show small inflamed bumps around hair follicles on the lower neck. This looks more like shaving-related irritation/ingrown hairs (pseudofolliculitis) or mild folliculitis than a reaction purely from the gold chain. I cannot diagnose it definitively from photos.

The brightening body wash could irritate or dry the skin, especially if it contains fragrance, acids, or exfoliating ingredients. A chain can also contribute through sweat, friction, or an allergy to metals mixed into gold, such as nickel. Jewelry-related dermatitis is usually itchy, dry/scaly, and follows the exact area where the necklace touches the skin. AAD contact-dermatitis examples

See a dermatologist or clinician if it is spreading, painful, warm, producing pus, you develop fever, or it does not improve within 1-2 weeks after stopping the irritating products. They can tell whether it is folliculitis, ingrown hairs, eczema/contact allergy, or less commonly a fungal rash and give the right treatment.