Buyer wants partial refund after 30 days?

I sold a shirt to a buyer on the 2nd of December and it arrived to him on the 14th (weather delays) and now he messaged me today, (January 15th) which is over 30 days wanting a partial refund claiming the shirt is dirty, has color fading and slight cracks on it. For all I know he could have done it to the shirt himself and is simply lying to get money back. Do I have to refund him? or since it's been over 30 days I can just deny his request, right?

Update: He's threatening to leave a negative review, anything i can do to counter this?