That is Russian propaganda.
Ukraine had physical possession of nuclear weapons in 1994. That was the whole purpose behind the Budapest Memorandum. Ukraine agreed to give up their nuclear weapons in return for "security guarantees".
Ukraine did not have the codes, they were in Moscow.
Ukraine had scientists who worked in the Soviet nuclear program.
They did not have the economy or the political will to maintain a program with nuclear weapons in the '90s.
They never had operational control, nor a Ukrainian nuclear missile force.