Stupid fingers is used in reference to
someone who has difficulty with
small tasks that require competent use of their fingers, such as typing, knots, putting
small parts together, etc.
Not to be used when someone has trouble with something that requires very skilled use of their fingers, such as an playing an instrument.
Kevin types so slowly, he must have stupid fingers.
Scott definitely has stupid fingers, did you see how
long he took to untie that knot?