I am new to arduino and I have a project that involves playing certain sounds according to the readings of five flex sensors, is it possible to connect an uno or nano to your phone via bluetooth to make it play certain sounds (individual letters of the alphabet)? All help is appreciated!

It is certainly possible to connect an Arduino to a phone using Bluetooth. If you want the phone to play sounds when it receives the data you will need a suitable program on the phone and writing a program for a phone is outside the scope of this Forum.