Good for you to be thinking about your future. Your questions is almost impossible for a stranger to answer, but I'll try. You don't say where you are in high school, so that makes a big difference if you are applying to colleges this year or in 3 years. If your school or local library has a career center, I'd start there to research careers that fit your interests. Nursing is a great profession (my mother was a registered nurse), but it is a commitment of time, energy and money.
One thing to keep in mind, most high school students aren't sure what they want to do, either. Many students really decide when they get to college and they have to pick a major. So it seems that you ahead of the game and have narrowed down your choices already: you have an interest in science, in helping people, in healthcare, and in art, so I would start with these interests and develop them through after school clubs, volunteer work, and part time jobs.
One field you might investigate is the field of Art Therapy, which combines healthcare and art. It is a relatively new field, but Mrs Pence, the wife of our vice president, is an art therapist, so it is getting more attention these days. Art Therapists work with children and adults and use art to help them deal and explore psychological issues in their lives. Art Therapists work in schools, hospitals, nursing homes, other healthcare facilities, and in private practice.
I hope this helps. Best wishes!