India has a nuclear program supported by the United States to counter the Soviet power in its neighborhood,
India and US have a trade deal in 2005, but India's nuclear weapon is built on their own and US tried to bully India with sanctions when Indian government tested their nukes but they played smart and did the smiling Buddha (Pokhran test) without knowledge of other governments. That is also the reason Pakistan wanted to have a nuclear weapon as soon as possible and they built their own a couple of decades later.
There is absolutely no nuclear programme "built on their own" other than the original Manhattan Project in the US. All other programmes were copied to a large extent and countries that were interested just found the way to get their hands in the secrets of it.
It is in fact more difficult to have a proper missile programme. The technologies involved are more advanced, more difficult to master, but you do not need fissile material for them.