Check your bass is set up
properly too and you haven’t got really heavy strings on and/or really high action/high neck relief.
There will be some discomfort until your fingertips build up some hard skin.
I’d really recommend using double bass fingerings in the very first frets (fingers 1, 2 and 4 over a 3-fret space) as it’s a much more comfortable spacing, especially if you have a small hand span.