Joseph P. Kennedy II said today he regrets not seeking the U.S. Senate seat vacated by his uncle, but the former congressman has no plans to run against U.S. Sen.-elect Scott Brown in 2012. Kennedy, who was in Brighton today delivering heating oil for his nonprofit Citizens Energy, was asked whether Brown’s victory made him regret his decision not to run to succeed his uncle, the late Sen. Edward M. Kennedy. “The thought has crossed my mind,” Kennedy said with a chuckle yesterday. “Maybe that wasn’t the greatest decision I ever made.”