Not quite technically true. Pakistan is one of only 7 countries to currently acknowledge having nuclear weapons and to have successfully tested them where the results have been observed by other nations.
South Africa had nuclear weapons and tested them, but voluntarily destroyed them during the 1990s.
Many other nations are capable of building and detonating nuclear weapons. It is known that Israel has nuclear weapons. North Korea is thought to posses them.
Others could quickly build them, Canada, Germany, Austria, Ukraine, Japan, Austriala, just to name a few. These countries choose not to build nuclear weapons.
More countries build both ballastic and cruise missiles than just five.
Now, this is not to take anything away from Pakistans technological acheivements, as they are very high, but too many people and nations place too important an emphasis on testing a nuclear weapon. A nation can be great without having nuclear weapons.