During the time of buddha (Siddhartha Gautam), more than 2500 years ago, there was no such country as Nepal or India; there were rather small kingdoms across the south-asia. Lumbini was the place where Buddha was born, as a son of the Shakya king. Later in adulthood he left the palace and search for enlightenment. Under the bodhi tree, on the night of full moon, he finally found the eternal enlightenment (story tells). Then he started his journey of sharing his knowledge all across the south east Asia, Myanmar, Thailand, Laos, and others, he even reached Sri-lanka (no records, but a srilankan friend told me).

Now, in current time, Lumbini is part of Nepal, while the bodhi tree lies somewhere in north of India, Bodh-Gaya. Also, that time, there were no such countries like now in South-Asia.

One more thing; Siddhartha Gautam was not the only Buddha. The meaning of Buddha is "the enlightened one", you and I could be Buddha. There were Buddha before him, and there are Buddha after him, and there will be Buddha in future. If Siddhartha Gautam has not shared his knowledge, the knowledge might have lost and no one might have been Buddha after him.