Check with your employer if they will help with your continued education somehow. My employer, for example, will reimburse some tuition costs if you get a degree while working there.
As a nurse you can continue up to and including a PhD. Or you can go to medical school and become an MD. There are many options. Try to find a few that sound interesting and learn more about them.
If you feel you have unused potential, maybe making a change in your career is just what you need. Even if you just look into what it would take, it could put things in perspective for you.