In F1 (and probably other motorsports) there is the blue flag rule. When a car is about to be lapped, they are shown a blue flag, and must give the lapping car an occasion to pass them at the earliest convenience.
I always read this as you can't fight for the position; you let them pass, and not cause an accident.
But if, for instance, you start doing better lap times with some fresher tires. Then you can't unlap yourself as far as I understand. You can't go up to the car that has lapped you before, because you can't really pass through him, you shouldn't fight for position against him (and risk an accident).
So even if you do faster lap times, are you stuck behind the car that has lapped you, or is there a thing that lets you pass the car that has lapped you?