There are apologies and there are official apologies, but the one former U.S. ambassador to Norway Mark Evans Austad received from the satirical British magazine Private Eye is a full-front, 1 1/2 grovel. When Austad, a well-known former Washingtonian with radio-television, business and political ties here, was in Oslo, his outspoken comments and activities frequently made headlines. In 1983, he was involved in an embarrassing incident when a Norwegian woman called police because the ambassador was pounding on her door in the middle of the night.

Austad had been at a cocktail party and a cab driver had taken him to the wrong address in a dark, virtually deserted neighborhood. Austad, who has had two heart operations, including seven bypasses, and who doesn't drink, said at the time he was frightened and added, "They're lucky they didn't have a cadaver on their doorstep."

Austad said yesterday by telephone from Scottsdale, Ariz., where he spends his winters, that Private Eye had admitted libeling him in a "Letter from Norway." The letter talked about that incident and several other things, including charging he had made racist comments. In its apology, the magazine wrote that its allegations "were without foundation and that their article constituted a most serious and damaging libel upon Ambassador Austad." And "to reflect the gravity of the libel and the sincerity of their apology, have agreed to pay Ambassador Mark Evans Austad a substantial sum by way of damages and to indemnify him for the costs . . . "

Under the name Mark Evans, Austad had been the host of several popular Washington radio and television shows. He was the chairman of Richard Nixon's 1969 inaugural ball and vice president of Nixon's 1973 inauguration. He was also a vice president of public affairs at Metromedia. Austad would not comment on the size of the libel settlement. He said, "I had enough to buy a beautiful painting to remind me of their asininity." More Celebrity Art Lovers

They had a busy morning again at the National Gallery yesterday. First Lady Nancy Reagan had a private tour of the Impressionist show in the West Wing that began just as the gallery was opening. Other visitors to the exhibition were permitted into the exhibition only after the first lady was several rooms into the show. Gallery Director J. Carter Brown and his wife Pamela conducted the one-hour tour. And for anyone who noticed that the first lady was limping, she banged her right big toe in the morning doing her exercises. Her press spokesman Elaine Crispen said Mrs. Reagan called off a tour of the Winslow Homer exhibit because her foot was bothering her.

At about the same time, British actor Michael York and his wife Pat were in the East Wing of the gallery. They made a special trip to Washington yesterday morning to visit "The Treasure Houses of Britain" exhibition. They had flown in from London and were on their way to their home in Los Angeles. York had finished a mini-series in Australia called "The Far Country." They toured part of the show in the morning, then went to the British Embassy for lunch, and returned later in the afternoon for the remaining rooms and the Homer exhibit. The well-known actor and his wife wandered through the rooms generally unnoticed in the morning but after three hours there in the afternoon, they were discovered by a few autographer seekers. Pat York told gallery spokesman Neill Heath that the Yorks have a private collection of theater, opera and ballet art that ranges from old master drawings to works by David Hockney. End Note

On most mornings when he is in town, super lawyer Edward Bennett Williams usually stops by the Jefferson Hotel, which he owns, for a 7:30 breakfast. On Wednesday morning he looked up from his table to see former attorney general Griffin Bell walk in and say hello. As they were talking another former attorney general, William French Smith, came in. Both were guests in the hotel . . .