The Bible does not explicitly say it is wrong to lust after one's spouse. Some might argue that lust, in its essence, involves objectification and selfish desire, which could be harmful even within a marriage if it becomes the primary focus. Others might argue that desire within marriage is natural and healthy, and that the focus of biblical prohibitions against lust is on desires directed outside of the marital bond.
Christian interpretations vary on this topic. Some emphasize the importance of pure thoughts and intentions in all relationships, while others focus on the context of marriage as a space for sexual expression and intimacy.
Ultimately, whether or not lusting after one's spouse is considered wrong may depend on individual interpretation and understanding of biblical principles.