I know how it feels needing to live with the imperfection. I guess if it's not too obvious, then just live with it. It can be quite cumbersome to replace door frames. HDB's bolted the door frames so well into the walls and floor, removing it will definitely cause quite a bit of damage. I was rather surprised how much need to be patched up after Ronald replaced the door frames to my bedroom. I learnt later that our HDB door frames are made of iron. I can only imagine how much more work needs to be done if you were to remove the door frame to the main door. Don't worry. You will get used to it after a while.