Slightly bent ball-screws are a somewhat common occurrence. It is not normally an issue In CNC milling machines and routers because the surrounding components are rigid.
You can straighten screws fairly easily with the correct tools. Some cloths, v-blocks, and an arbor press is the best option. Otherwise a vise plus a cheater bar (aluminum tube to go over the screw and use as leverage) does okay.
Mark the bend with a sharpie and go slowly.