Creases on floor

[Poconos]

Being as how it's only 1/3 full I'd drain and fix the problem. Since you drained it already and got away with it my guess is the liner isn't that old. I'm thinking the folds will cause problems down the road. Just my quarters worth.
Al
BTW: Welcome to the forum.

[matt4x4]

Folds that big will become algae traps and can be cause for concern when the automatic cleaner hangs up and wears at them, I would also fix it.
BTW - You're the first I've ever heard of that drained the pool due to algae.......