I assume tire pressures have been checked? Will it still spin with you sitting on the mower?
End of the day, a lawn is full of bumps and undulations so a slightly (1/8th) twisted frame (if thats what it is) probably wont cause to much of a drama. Probably sort itself out as the frame twists with use!
What can cause issues is a twisted deck!
If you are super worried about it, park the low wheel on a brick and put weight on the opposite side. Leave it like that for a week and see what happens.
Mowers are made out of many parts put together by people on low wages that go to work hung over or looking to get hung over. For the size of the problem (1/8th) I'd forgive.
Real problems start when things fail!
Check your tires, grab a beer and go mowing, dont stress about it!