I'm 64 yrs. Old & have problems with large pores on nose & chin which fill with blackheads; have tried retin a (tretinoin) did nothing. Would chemical peel help?

Rosacea. There is an adult variant of acne called "rosacea" which presents with large pores, oily skin, and redness of the nose, cheeks, and chin area. If this is what you have, other medications are likely to help, in particular, a topical antibiotic called "metrogel" or other oral antibiotics like Minocin (minocycline) or tetracycline.
Large pores. Dermatologist pore treatment methods are generally microdermabrasion, laser resurfacing, and chemical peels. Microdermabrasion uses microcrystals to remove dead skin from the skin surface. It can also unclog pores, removing whiteheads and blackheads. Microdermabrasion also results in healthy, clear skin. Topical medication includes tretinoin.
Large pores. Dermatologist pore treatment methods are generally microdermabrasion, laser resurfacing, and chemical peels. Microdermabrasion uses microcrystals to remove dead skin from the skin surface. It can also unclog pores, removing whiteheads and blackheads. Microdermabrasion also results in healthy, clear skin. Topical medication includes tretinoin.
Yes. A chemical peel could help loosen the blackheads and improve your appearance. You may still need to use a topical retinoid 1-2 weeks after the peel to maintain the effect.