FOR A BRIEF moment last week, it seemed at least conceivable that the crisis in Central America might be rising from the regional level toward the global level. The possibility arose that the Soviets were doing one of the few specific military things -- shipping advanced fighter aircraft into Nicaragua -- that the Reagan administration and a good number of people who are otherwise its critics have made plain they would regard as an unacceptable threat to American interests. The counter possibility then arose that the United States would react by force.

The week ended with no evidence that MiG21s were in the particular cargo whose passage had aroused Washington. No American military attack came. There was a great amount of smoke -- from Managua cries of alarm and of heightened distrust of a reelected Ronald Reagan and from Washington some military feints and gestures on the Nicaraguan periphery. But there was no fire. The sequence amounted to another chapter in a war of nerves that continues still.

It is possible that the Sandinistas, careful as they insist they are not to give Washington cause for direct intervention, may yet be led by inexperience, emotion or reckless calculation to raise the crisis to the great-power level. That leaves the more relevant question of whether the Soviets, who are not inexperienced and who are not ordinarily emotional or reckless, would step over the threshhold themselves: would step over it at a moment when Mr. Reagan's leadership had just been fortified and when otherwise he was testing the chances for diplomatic engagement on matters of major Soviet concern. It could happen, but it would be a great surprise.

Meanwhile, there is the real world, where the threat is not a possible quantum leap to MiG21s but the steady buildup of less dramatic arms in Nicaragua over a period of time -- arms of a sort that incontestably were in the cargo landed at Corinto. Those arms give Managua a capability to deal better with what it maintains is a large American threat to Nicaraguan interests. They also give it a capability to put pressure on its neighbors, if not now while the Sandinistas may be preoccupied domestically, then later when the United States may not be so attentive.

There could be no clearer demonstration of the need for a political solution. The Sandinistas doubt the Reagan administration's ultimate readiness to accept coexistence even with a moderated regime in Managua. Many administration officials wonder whether the Sandinistas can relinquish their revolutionary ideology for a focus on building a society acceptable to different Nicaraguans at home. But the political path for accommodation -- within Nicaragua, with Nicaragua and in the region as a whole -- remains open.