I planted a Norway spruce and now...

Depending upon how long ago you planted it, you can still adjust it if it was very recently. You can remove some of the surrounding soil and resettle the root ball. Gently repack the soil in around the roots when finished and water thoroughly to aid in the resettling. If you think it’s been in the ground long enough for the roots to have attached to the native soil, you may consider just leaving the leaning tree alone. Its top will grow straight up toward the light and in a few years will at least appear straight. We wouldn’t recommend staking unless the tree is in an overly windy spot.