My Son Fell On Concert 4 Months Ago. We Had

My son fell on concert 4 months ago. We had X-ray done and they said he was fine. It has started turning slightly gray so I took him back to dentist and another X-ray was done. There is no sign of infection and it doesn't hurt him yet they say he needs a root canal. They said if it gets infected he could lose the tooth and it will continue to darken He cannot feel cold on the tooth so maybe the nerve is dead but is a root canal necessary? I do not want to put him through this if there is a chance it will be ok.