If your kid is selected for a scholarship and is waiting for a DODMERB waiver/completed physical you can substitute a sports physical to participate in NSI. The form is included with the NSI paperwork and is also available here:
https://www.aap.org/en/patient-care/preparticipation-physical-evaluation/ .
My son was an alternate last year and was selected about this same time. Eager to go to NSI, he contacted his unit and got the NSI packet about four days later. He used the sports physical to attend NSI. He graduated and received his Navy BUMED waiver a couple of weeks later. Unfortunately, you can't activate your scholarship without having a qualified medical/medical waiver. The sports physical is just for NSI. The unit is really the best source for info and your child contacting them shows demonstrated interest. That actually goes for college admissions as well.