First I would call my PB out and tell him to fix it under his warranty. If he says cracking is normal, agree with him, because it is. Settling is not normal. The backfill area is notorious for settling. PB know that and should take that into account when backfilling. He needs to fix it for free.
Was your concrete poured in May 2013? How soon after they backfilled did they pour? What did they backfill with? Dirt? Rock? Road base? When did the concrete first crack in the control joint?
It may be that the entire area has settled and the pool side is resting on the walls, What does that joint look like? If its resting on the wall then you need to do something. Any settling anywhere else? The crack and settling is a concern, but the big worries are why is it settling and will that harm the pool structure.
As for fixes. You can replace that section of slab. Looks best-- costs a lot but cheap for the PB. Grind down the high side. Doesn't look so great and not something you should accept from a pool builder. There are other fixes but those are the ones that are reasonably well priced.
