Player messaged me telling me to report another player for cheating.

I would like to know what section to report this player for this message.

I was actually distracted by this message and made a blunder costing me the game.

I looked at the game that accuser played against the player who I was playing.  His opponent who had a higher rating made a lot of mistakes and got into time trouble in a worse position but was bailed out by the accuser who hung a minor piece and then a rook.  

Obviously there was no cheating in this game just bad play.  

Would appreciate any advice to deal with this unwanted and unwarranted message. 

Wait, how did he even get hold of your username in the first place?

He must have been watching my opponent play next game. I received notification while playing and then saw that he was mentioning the player who I played with.. I checked the history of my opponent who was accused falsely and saw that he played the accuser the previous game.

The site does not use bots in player pools.

This wasn't a chat, this was a message. I reported the player for spam and blocked him now. It's up to chess.com now to handle this as making accusations against players are not allowed afaik. People should just report anyone they suspect of cheating and that's it.