Light aircraft cargo pilot reported realizing after the flight that he flew an unauthorized approach into JER airport at night that probably resulted in a CFTT incident.

Narrative

Cargo and one passenger. I am filing this report due to my oversight in flying an RNAV approach at night that is prohibited at night. I have flown to JER many times in the past few months on my new job as single pilot IFR part 135. I am familiar with the airport and have landed both runways multiple times. I'm also familiar with the obstacles. On this morning it was clear visual to the airport from about 5-7 North as I descended and approached from ZZZ; there were clouds in the area and I was on IFR flight plan and could have landed visually except that I believed; there were likely clouds in the dark areas South and East probably blocking a typical Left pattern entry. (Cannot do right traffic on RW27) Winds were highly favoring RW27. On the G1000 I had dialed in the approach and asked for it; was assigned it; and flew it; mostly in the clouds. I flew this (autopilot fully coupled) from memory and off the G1000. Landed safely normally on RW27. I did not refer to the approach plate. A few days later realized that I had not given any consideration to the approach being NA at night. Had I referred to the plate instead of being in a hurry and merely loading the approach into G1000; I would have stayed VFR or diverted. This is a big error because the antennas and barn East of the approach end of RW27 are seriously close and I have avoided them visually prior flights. My error was in assuming. I was lucky I knew the airport; and cannot imagine doing something similar at an unknown airport without fully briefing the plate. I learned the stupid way that I must fully brief the plate each flight even for familiar airports.