Typically, what happened is that water IN the GROUND got higher than water in the POOL and lifted the liner off the bottom. Then, when ground water level dropped, the liner settled back down . . . but with wrinkles. Unfortunately, the solution involves having pool techs who know how to install a liner, drain the pool and then reseat the liner.
You'll want to schedule the work now . . . but for warm (hot!) weather. Used liners are less elastic than new ones, and you'll need the heat to get the liner in place without ripping. Fortunately, with a liner only a year old, it should still be possible.
By the way, you can find answers to questions like this, using my new 'Super Search' page: http://pool9.net/ssearch/. Here's the link it created for "wrinkled liner":
https://www.google.com/search?q=%28s...0liner+%22+%22
If you use it, there are a number of other posts and pages discussing this problem, and possible solutions.
Good luck!
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