Mary Decker electrified a crowd of 18,293 at Madison Square Garden tonight as she ran to a world indoor best in the women's mile at the 75th Wanamaker Millrose Games. But she says the best is yet to come.

In winning the mile in 4:21.47, Decker, 23, was timed in 4:03.6 for the 1,500, slightly under her record time of 4:00.8 set two years ago. Her mile time erased by more than three seconds the mark of 4:24.6 she had established at Los Angeles on Jan. 22.

"I felt strong. Not being tired at the end was a good sign that I can go even faster," she said. "I wanted to run two seconds faster. I was looking forward to 4:20."

Decker, who last week bettered two indoor bests in the same meet--in the 2,000 meters and 3,000 meters in Los Angeles--sped into the lead from the opening and never was challenged. She pulled rapidly away from the strong field that included two-time Millrose champions Francie Larrieu and Jan Merrill, plus intercollegiate champion Leann Warren.

Decker almost did not get on the track to compete. Just prior to the race, she said an official shoved her and told her to leave the track.

"I was real upset because he nearly threw me out of the building," said Decker. "People around him told him who I was, but he said, 'I don't care,' and he pushed me.' "

In the pole vault, Earl Bell beat world record holder Billy Olson with a leap of 18-6 1/2. In other major events, Don Paige took 10 seconds off the Millrose record in the 1,000 meters--the first time this event has been contested since 1933--with a clocking of 2:20.42; Steve Scott won the mile in 3:55.37 and Milt Goode and Dwight Stones each cleared 7-7 in the high jump, but Goode was declared the winner on fewer misses.

Earlier, sophomore Candy Young of Fairleigh Dickinson and Stephanie Hightower broke the world indoor best in the women's 60-yard high hurdles with dead-heat clockings of 7.38 seconds.

Young and Hightower had shared the previous best of 7.47.

Chandra Cheeseborough lowered Garden and Millrose records and missed the world indoor best by a 100th of a second in winning the women's 60-yard dash in 6.61.

Like Cheeseborough, Renaldo Nehemiah ran the second-fastest indoor race in his event, overpowering the field in the men's 60-yard high hurdles in 6.84 seconds. Only Nehemiah's 6.82 two weeks ago in Dallas was better.

Nehemiah, however, set Garden and Millrose records, breaking the marks of 6.89 and 6.90, respectively. He had held both.

Carl Lewis, an indoor record holder (28 feet 1 inch) in the long jump, broke arena and Millrose records in winning at 27-7 3/4. It was the Millrose's first long jump competition since 1969, and meet director Howard Schmertz said it was done strictly because of Lewis.

In the men's 600 meters, Fred Sowerby of the D.C. International club (1:09.82) finished second to Antoine Blair (1:09.04).