Lease of apartment before the will is probated

Simple synopsis: •My father owned a self made/ self-owned flat in a CHS in Colaba. •He passed away around 18 months back. My mother passed away more than 15 years ago. •We are a Hindu family of 4. (My father, mother (mentioned above), my sister and me). •The flat was nominated in my favour and based on the nomination, the Society transferred the share certificate in my name •There is a proper Will of my father which also mentions that the subject flat has been bequeathed to me. •There is no dispute between my sister and me. She has given an Affidavit that she has no interest in the flat and the said Will is genuine and she does not contest the Will or the Nomination. •There is no other dispute, no claim, no letter registered with the Society on this matter. •The dues are all paid and clear. The Society MC has advised that until and unless the Will is probated, I (as a nominee) cannot lease out the apartment and they will not issue a NOC. What is the law on the subject?