SW validation neccesity is always derived from the intended purpose of the SW.
So, first understand, what is the specific purpose of the SW in your process or process task? (without this, your validation will not be focused)
If the SW is used for e.g. electronic recording/archiving, electronic signatur, or for automating process steps (without human control possibility),
then you typically need to validate it (for the intended purpose in context of your process).
The whole approach of SW validation needs to be conducted based on an established QMS procedure (important: risk based).
As already indicated, ISO TR 80002-2 may be very helpful for this topic.