Is a fat upper lip treatable that resulted from a punch to the face? (Photos)

My best guess is your injury caused a laceration that was not repaired or was repaired without correct anatomic alignment at the time of injury.
If the tissue edges heal together in a non-aligned manner then this could change your lip contour.
In certain circumstances it’s possible to try to re-create the injury surgically and realigned the edges in the more anatomic manner.
Easier said than done and probably not advisable for most people.
It may be possible to excise lip tissue to try to make your lips more symmetrical but most likely plastic surgeons would lean towards not intervening just like yours did.
Often it’s very difficult to see malalignment or scar tissue at all the way lips heal.
I guess in situations like this an ounce prevention goes a long ways but that is playing Monday morning quarterback isn’t it.
I suppose it’s also possible to inject filler’s in the opposite side for the sake of symmetry.
Most likely your best option is to leave things the way they are
Best, 
Mats Hagstrom MD