My brother sold our joint family land in Pune without telling me?

I recently found out that my brother sold our joint family land in Pune without my consent. We inherited it from our father, and I was never informed about any sale discussions. The sale happened two months ago, and I only learned about it when I tried to visit the plot last week. I'm feeling betrayed and worried about the legal implications. Is this sale even valid? What steps can I take to challenge this?