Your child will eventually get over it, it just takes time and perhaps counseling to work through the anger. I left when I was 27, and was bitter for a few years. However, I realize my parents made the choice to be JWs when they had me because they wanted to raise me differently than how they were raised, and hoped to shelter me from drugs, and the crazy lifestyle they previously led. They succeeded in that, and I am grateful for how my life turned out, despite some of the issues of being raised a Witness.
However, I also realize that everyone has problems. There is no perfect life, or perfect way to raise a child. Being raised as an atheist or different religion wouldn't have protected me from experiencing hurt in my life. I would have had different experiences, but still would have had difficulties to work through as well.
If your child is upset about not playing sports, perhaps they can play drop-in sports now. Or maybe they just felt isolated, and need to work through that. Other people feel lonely or like outcasts too, despite not being raised as a JW.
My parents apologized once to me, and that was enough. They were just doing what they felt was right at the time, and had my best interests at heart.
One day, when your child has children of their own, they might understand better. Don't be too hard on yourself! There is still time to enjoy life to the fullest.