Uneven Panel

[Shearhair]

Hi I'm new here and new to quilting. I have a question, before I return the panel I purchased at fabric depot, I
Pre washed my fabric and started on my quilt i noticed the panel is way out, even if I was to cut it into sections it will still be uneven. The other panel was fine. Did I ruin it by washing it first? I'm afraid they won't exchange it because I pre washed. The reason I pre wash is because I was told different thread counts shrink differently. Is there anything I can do to fix it? My husband and I looked and measured and it's a few inches out and there is no way of evening it that we can see.