You should have filed Form 1040, not Form 1040NR, for 2014. You are a resident alien if you meet either the substantial presence test or the green card test. Once you got your green card you became a resident alien, because you met the green card test, even if you didn't meet the substantial presence test. Even if you were not a resident alien before you got the green card, you should have filed Form 1040 as a dual-status alien for that year.
However, it's too late to file an amended return for 2014. (The deadline was April 15, 2018.) If you haven't gotten any notices from the IRS about your 2014 tax return, I think you should just forget about it at this point. Don't do anything, and don't worry about it.
