TOKYO — Sanctions aimed at punishing the North Korean government are hampering the ability of aid groups to operate inside the country, triggering warnings that the international campaign is harming ordinary North Koreans. Difficulties in obtaining supplies, including medical equipment, and in transferring money to fund aid programs could have a direct impact on health and nutrition levels throughout North Korea, they say. “We need to deal with the nuclear problem, but we need to properly ponder our means for achieving that goal,” Tomas Ojea Quintana, the U.N.’s special rapporteur on North Korean human rights, said in an interview in Tokyo.