Brother sold our Mumbai flat without informing me, what legal steps can I take?

I recently found out that my brother sold our jointly owned flat in Mumbai without my consent. We both inherited the property from our parents, and I was living abroad at the time. I only got to know now because I received a notice from the buyer's lawyer demanding I vacate. This feels like a massive betrayal and I am not sure what to do next. It’s causing a lot of stress. Can I challenge the sale or get my share? What are my options under Indian property law?