Message to concertgoers in Mansfield: When you see a tour bus driving in your direction, stay out of the way. The failure of a Kings of Leon fan to do that after the band’s concert Saturday night at the Xfinity Center forced the band to postpone a show the next night in Saratoga Springs, N.Y. “The band was en route to their hotel after their show in Boston when a pedestrian jumped in front of their tour bus, causing the bus to stop short, injuring Nathan Followill,” read a message on the group’s website. “Nathan is being treated for broken ribs, but is doing well.” Nathan, one of three Followill brothers in the band, is the drummer. (Kings of Leon includes siblings Nathan, Anthony, and Ivan, and cousin Cameron Followill.) Followill didn’t sound too upset when he tweeted to fans afterward. “Thank you for all the get well soons,” he wrote, “I’m a little banged up but will be back better than ever.” The band’s next tour date is Wednesday at Jones Beach Theater in New York.