Is a 3.0 GPA good in nursing school?

A GPA above 3.0 would be a good GPA for nursing school. That's the requirement for some programs. If you have aspirations for graduate school, you might need a GPA closer to a 4.0, depending on the school or degree you want.

Does GPA matter after nursing school?

GPA matters in nursing school, but not the way most think. It matters because of your program requirements, scholarship requirements, or if you want to go to grad school later. As for getting a job, I think you can get that regardless of your GPA.