Don’t worry about being behind. Sophomore year is still a great time to start internships and entering competitions. IMO, this is the time to really try and figure out what you want to accomplish in high school because next year you’ll be swamped with APs and SATs…
NIH is extremely competitive and especially since you mentioned that you haven’t had lab experience (I’m assuming?) I suggest finding a local university to do research. Start by searching up which professors’ projects interest you and try to become informed on their topic of interest. Either that or you can propose your own project. Email them explaining your intentions on interning or shadowing and that you have not had prior lab experience. It will be tedious but it’ll be worth it. As for hospital volunteering, many positions are only 18+ but there are definitely jobs that high school students can assist in.
Here’s a helpful link that might apply: http://talk.collegeconfidential.com/high-school-life/1629448-teamrocketgrunts-general-guide-to-getting-involved-in-research.html
Good luck!