Is Succession Certificate is essential?

My mother (63 years old) recently passed away (2nd October 2015) without executing any will. I'm my mother's only child (son). My mother had a small shop. Currently me (21) and my father(72) running that shop. But to run business we need to get access to mom's savings account (as she done every transaction and payment using her personal savings account and had no current account for shop). And what worse, we found out nomination for that account is blank, or more accurately that nomination procedure was not complete. Now we decided that we'll transfer the remaining balance on my mom's account on my account (I've an savings A/c. on same branch). But operation manager denied to listen any thing and asked to bring succession certificate. I checked latest balance on my mom's A/c. it was only Rs.7644.40. Now my question is did I really have to produce 'Succession Certificate' to get that small amount or there is another way? because I can guess getting succession certificate will be costlier than this. My dad has full support on me, as we have no other member on our will it help me to clam mom's account and change trade licence name? Please answer, it will be a big help.