There's no problem. You don't have to do anything special. Just enter your son as a dependent on your tax return. Yes, TurboTax Premier will walk you through it.
If your son is in college I assume he is over 16, so you will not get a recovery rebate credit for him. It doesn't matter that he got a stimulus payment based on his 2019 tax return.
If your son files a tax return for 2020, make sure he indicates that he can be claimed as a dependent by someone else.
