Father awarded sole custody

I won my child custody case and was awarded child support in Florida in 2008. Mother took child to Texas in 2007. I was unable to get Texas to turn child over to me. Just this week I received a first ever child support check for over $5000. I have never had the child and mother won't let me see or talk to him or herself. Can I legally keep this check and put it in a savings account for him or do I have to surrender the check back?
Thank you.