NIC voluntary contribution and ILR

[Saragaso]

Hi I'm on Tier 2(General) and due for my ILR later this year. When I was on PSW prior to Tier 2, I had received a letter from HMRC in 2012 advising me of a gap in my NI contribution for the year 2010 and that the payment was completely voluntary.I've been in regular full time employment since 2012.The letter said I can make a payment till 2019.
When I try to make a payment now I'm advised it by Department of Work and Pension that it may be futile as it may not contribute towards my pension fund post retirement after 29 years. Can anyone please advise if I need to clear this prior to my ILR? Im repeatedly told my HMRC that the payment is not mandatory and hence should think twice before making it.Thanks