Unless your tap water has an unusually high level of chlorine, it is extremely unlikely that any harm was done, especially with a small water change like that. I know lots of people who do 50% water changes without adding dechlor, and have been for many years without issue. I only started using it a few years ago when I obtained some inexpensive crystals of sodium thiosulphite to make my own.
Join a fish club. Don't have one in your area? Start one.