Is my tooth nerve dead?

Okay.. It all started when I was 9 and I rode my electric scooter like really fast into the trampoline.. (I was small) and my 2 front teeth fell out.. Now 4 years later.. I went to the dentist and he said my nerves had died and had to be treated.. He said that it will turn into diff color and might get an infection.. He asked if my 2 teeth hurt or feel weird.. I blurted out yes without even thinking and he said ok.. I lied.. It didnt hurt or feel weird they were both normal like my other teeth and the color is also normal.. Help? He said I needed to get it treated when I get older..