Dr. Toyin Ajayi has an ambitious mission: to make health care accessible to all. Ajayi is the founder and CEO of Cityblock Health , a primary care provider focused on helping underserved communities in the U.S. She's not fazed by the enormity of her goal. "All the things we enjoy and take for granted today didn't exist [at] one time. Someone dreamed them into existence," she says. Having "a sense of confidence and agency" is the key to tackling complex issues, Ajayi told CNBC's Julia Boorstin