My cousin sold our grandfather's land without informing me. Is this legal?

I live in Pune and found out last week that my cousin sold our grandfather's ancestral land without telling me. We both inherited it, but he never discussed the sale with me. The property is valued at around ₹50 lakhs. I'm feeling betrayed and unsure of my rights. Is this sale even legal, and what can I do to challenge it? I need urgent help to understand my position.