Bhagwan Mahaveer Swami is a Siddha now.

In Jain Dharma this means:

• He has no physical body now.
• After attaining Kevaljnan (omniscience), he finally attained Moksh (Nirvana) at Pavapuri (in present-day Bihar).
• From that moment, his soul went to Siddha Shila – the highest state at the top of the universe, where all liberated souls reside forever.

So:

• Historically (on earth):

- Birth: Kundagram (near Vaishali, Bihar) - Nirvana: Pavapuri

• At present (spiritually):

- Bhagwan Mahaveer is in Siddha Shila as a pure, liberated soul, beyond birth, death, happiness, or sorrow.

You can read a simple explanation about Mahavir Swami here