dear Souparna Dan 

greetings,

do not panic, there are many people who forget their application number but it is very easy to recover. just go to www.cbseneet.nic.in then under the column of online services you will find a " Forget Registration Number" clikc on that and enter the details after that you will get your application number on your email id. 

kindly comment below if you find difficulty. 

Note: sharing Aadhar card number on any kind of social site will attract you a lot of trouble.