Depends on how bad it is, really. All you can do is fly it and see.
It "could" impart significant "rudder" action on elevator application,
and if it's bad enough, it "could" even require a lot of rudder to trim out,
even to attain "straight and level flight". If you're going to be practicing pattern,
tear it down and fix it right. If you're just sport flying, and one side isn't
more than about 3/8" below the other, you probably won't even notice it that much.

Truthfully, I've flown planes that were even worse off than that.
I repaired a swizzle stick once, in my early RC days, that had to be off by an inch.
I honestly couldn't tell much difference in flight, once I had retrimmed.
Fantastic plane, that one. It also had the covering ripped from both inside
rib bays, from me constantly folding my gear up. After the second time, I sealed
the pieces to the inside, and flew with the inside bays "open" because I was lazy
Well, that, and I just pretty much sucked at landing, back then.