No you don't need to do that.
the last point for you to do that is in reply to the summons or at the exchange of evidence.
If the witness to your careless driving is the other driver, then it cannot be relied upon as he was involved in a road traffic accident with you and failed to stop. He is an unreliable witness.
There are certain circumstances where the NIP can be deemed valid, but they are unlikely and you still have to comply with the request (as you did). It simply cannot be used as evidence and therefore there is no basis to prosecuted you, unless the magistrate (wrongly) thinks otherwise.
What you don't know is if he did report to the police the accident.
It would be wrong to advise what to say, if you are interviewed. something along the lines of "its all a bit hazy as you contacted me so long after the incident, I remember some bloke in a xyzzy driving too fast and clipping my car causing some minor damage, was this the person alleging the careless driving? Surely thats not an independent witness? Are you able to give me his name and address so that I can recover my damages?"
obviously they wont. but there is enough hints in there for a CPS review to fail.
You may find the section on careless driving worth reading..
www.cps.gov.uk