Unless you raised this with purser on the flight, you will have troubles to prove your case and to get any compensation. If you did raise it with the purser, (s)he should have offered you compensation on the spot (or you could have asked) in the form of points or in-flight vouchers... If you did not, probably tough luck...

While I acknowledge this did happen to me on LH flight (not TG), I received immediate offer of reasonable number of M&M miles which I accepted. Later on, after reading some reports on M&M, I realised that purser gave me most he could, but some people got more, so I then complained to LH and received further amount of miles... The important point being, that for purser to give me any points he had to make the report, so I had a proof of non-functioning seat...