I just recently got the pmdg 737. I have done the first tutorial flight only two times now. On the 2nd time I did the first tutorial I got the message saying nav out of date on the fmc. I just cleared it out. But I am not sure if this is gonna effect future flights? Thanks.

If you want up-to-date NavData, you must purchased the latest version (Airac Cycle 1407 just released today) from a company like Aerosoft or Navigraph.

or simply just ignore it  if you don't  want  to upgrade  it

It will NOT affect your future flights, as it's just a reminder for your nav database not quite being up to date with the current real world navdata cycle.

 

If you buy a current cycle, the message will again start popping up in four weeks the latest - just what would happen in the real plane as well.

 

Buying cycles is for people who want to have a homogenous database across their planes, offline ATC, and flight planning tools. And/or for people who fly online or use current (paper/online) charts.

 

No harm will be done as long as you are happy with the data currently contained in your FMC.

Okay that's good. I'll just clear it out everytime then thanks.