Joining new PSU without Noc from previous PSU

R/Sir
When I was unemployed, I appeared in the interview of two central govt. PSUs {let the name of PSU be ‘X’(Miniratna Company) and ‘Y’(Maharatna Company)} and got selected in ‘X’. I had joined ‘X’ with all the basic formalities by signing the bond for serving at least 4 years and if failed to serve, I have to return 03 month salary and many other conditions. ‘X’ has issued my joining letter after some days of joining, but after 20 days of joining I had also got selected in ‘Y’ also. I had decided to join ‘Y’ and resigned from ‘X’. Since without NoC from previous employer I was not supposed to join ‘Y’, so I had decided not to disclosed my previous employer detail in attestation form because I am not having NoC from ‘X’. I had completed one month in ‘Y’. My query is that, if by any means ‘Y’ came to know about my previous employment with ‘X’, can any action against me will be initiated?? Or could I submit NoC of ‘X’ after few months, because ‘X’ will issue NoC when I will pay 03 month salary as per T&C of bond. What will happen if I will submit NoC after any action against me???