The Soviets have to get nukes on their own. It will happen, but it will happen a lot more slowly. This probably averts a lot of the Red Scare, but the scary possibility is this - more nukes used. If the USA feels it can threaten the Soviets or Red Chinese without fear of retaliation, it's going to.
It depends what you mean by "a lot" more slowly. David Holloway, *Stalin and the Bomb: The Soviet Union and Atomic Energy 1939-1956* (Yale University Press 1994), while acknowledging the major role played by espionage, adds (p. 366):
"The best estimates suggest, however, that the Soviet Union could have built a bomb by 1951 or 1952 even without intelligence about the American bomb. There already existed in the Soviet Union strong schools of physics and radiochemistry, as well as competent engineers. Soviet nuclear research in 1939-41 had gone a long way toward establishing the conditions for an explosive chain reaction. It was because Soviet nuclear scientists were so advanced that they were able to make good use of the information they received from Britain and the United States about the atomic bomb."
https://books.google.com/books?id=ICO6aUnQ2KcC&pg=PA366
I suppose that it could be argued that if the Soviets didn't have the bomb by 1950, they wouldn't have finally gone along with Kim Il Sung's pleas to let him unify Korea by force:
"Following the meeting with Kim, Zhou visited the Soviet Ambassador Roshchin seeking clarification and an explanation in Stalin’s decision to support the North Koreans.250 Stalin was likely aware of Kim’s trip to China and prepared for the subsequent question from the Chinese leaders. His reply to Mao was sent less than six hour later. In the May 14 telegram, Stalin explains that “in light of the changed international situation, they agree with the proposal of the Koreans to move toward reunification.”251 There is room for doubt in what Stalin meant by ‘changed international situation.’ Since Stalin’s previous September 1949 denial to support Kim’s reunification, several changes had occurred that could have led toward Stalin’s shift: *successful testing of a Soviet atomic bomb*, the Sino-Soviet Alliance, and changes in American foreign policy toward rearmament.252 Stalin does not specify in his response to Mao the reason for the change, but again emphasized that any decision “must be made jointly by Chinese and Korean comrades.”253 This response continues Stalin’s plan to avoid direct Soviet involvement in Korea." [my emphasis--DT]
http://calhoun.nps.edu/bitstream/handle/10945/44622/14Dec_Monger_Bradley.pdf
I am doubtful, though, that the Soviet bomb was really the decisive consideration with Stalin. Even if the US still had a nuclear monopoly, he would probably not believe that it would use it against the USSR over the Korean issue, as long as Soviet involvement in Korea was mainly done through proxies.