I'd still book in to the dealer to report it - much as this is evidence, it could be evidence of you knowing something was wrong and not giving the dealer chance to rectify it. Once it gets worse the question I'd ask (if I were the dealer) is "If you knew it was like this x months ago, why didn't you report it?"
Also, remember the warranty on trim and/or cosmetic items isn't as long as the normal warranty.
I only say this as we all know how some dealers will attempt to wriggle out of anything they can these days (or is that just my cynical outlook on life?)