My uncle sold our shared Mumbai apartment without informing me?

I recently discovered that my uncle sold the apartment we jointly inherited from my grandfather in Mumbai. He never informed me or sought my consent. I've been residing in Delhi and had entrusted him with the property's upkeep, but this was a complete shock. The sale happened six months ago, and I only found out when the new owner visited the flat. I'm deeply hurt and unsure of my legal standing. Can I challenge this sale and what are my options to claim my rightful share?