Welcome back, first and foremost.
Let’s get to the question, including some spoilers:
you’ve joined in a pretty good time. Shadowlands is just around the corner. Anyone that dies goes into the maw (mega hell). If you watched the cinematics (Uther) you will see that he didn’t go to some light paradise, but instead to the weird blue people. Means one of the highest paragons of light didn’t get what many thought they would, namely a light heaven.
This could play in your paladins character as a huge dilemma.
Killing someone or in the past in the names of the light / war or whatever means you sent them to mega hell. One of the highest light paragons didn’t get the good light heaven that many characters might have believed in.
This might create some religious doubt, even for your paladin character.
All of this only comes up when Shadowlands is released though, so don’t do anything too quickly now.
Over all the implications are, imagine your paladin who maybe just wants to do good and only kills when it’s absolutely in self defense.
Whoever you killed? Congratulations, you did sent them to an eternity of torment.
Here’s the thread about it. Maybe you can draw some thoughts from there to your character. 
On another note:
now that the war is over, your character may try to help the places that were hit by the war or, a very simple task, offer talking sessions in Stormwind to those who are in need. Try to establish friendships crossfaction. Establish a church in Booty Bay (because why not, right?) or try to establish a place in other places of the world, perhaps other hubs? Duskwood (pls no deus vult let’s purge this place of all evil), Booty Bay and Redridge are all zones with active roleplaying communities / people traveling by, Westfall as well but I am not sure if the local Defias guys there want you there. 
Depending on how much your character is with the light, you might seek for him some conversations out with lightforged or even ren’dorei to understand the other side better.
Dunno, there are a million options really.