He was bored, yes, but there was a second purpose to this. Ares was useless at finding people. Ruining their day and making them bleed, yes he was excellent at that. So he'd seen the opportunity in Hermes' spat with Achilles and took it.
He wasn't close to Hermes, none of the sons got along particularly well, but this suited him just fine.
So when he arrived to Achilles new address, he waited just long enough for the door to open before greeting Achilles with a punch to the jaw. Hard enough to knock him to the ground. "Should feel lucky kid. You remember all I am? You remember the bloodlust of Troy? Lucky I ain't making you feel so much of it that you tear apart the bitches you're keeping safe. All I got issue with is you today."