Bosley was among a handful of Chicago youth who joined students from Stoneman Douglas High School in Parkland, Fla., where 17 people were killed last month during a mass shooting.
About 850,000 people attended the D.C. rally.
"I'm not going to lie, I was nervous. My plan was to look past the crowd, but the crowd never stopped," Bosley said.
Bosley talked about the murder of his eldest brother, who was shot while leaving church on April 4, 2006.
Beyond the marches, he wants to see young people take action, including registering to vote.
"We need people to vote in our communities," Bosley said. "We need resources. That's really big because you can't get people off the streets, jobs or anything like that unless we have the resources to do so."