Sorry to say but you will just have to wait, even though the IO told you he was going to approve you there are other steps has to be taken like a supervisor has to look over your case uscis has 120 days to make a decision I was well over my 120 days before I got my n-400 approve and oath ceremony.I had to do 2 interviews one for n400 then the other for 751.so be patient your approval will come at their own convenience