Change internal voltage reference on an STM32L0
You can't change the internal reference voltage, \$ V_{REFINT} \$, as it's a band gap device fixed at about 1.22V. But the ADC range is from 0 to \$ V_{REF+} \$ anyway, and unless you have a pin available for \$ V_{REF+} \$, which you probably haven't on the version of that processor fitted to the Nucleo board, it will be tied to \$ V_{DDA} \$

The only option would be to amplify the voltage from your sensor. Alternatively, use a digital sensor you can read directly by I2C or SPI.