All sorts of parts on a car break in. Brakes, transmissions, suspension, etc..
You engine has a non linear curve concerning break in. Massively more wear at 100 miles than 1000. And less and less as it goes on. Some wear always occurs as miles rack up, but it is extremely diminished.
By 5,500, all systems are good to go.
If you are concerned with your first oil change, now is a good time. I would like to see the first fill flushed out by now.