As long as you defrosted it the safe way (under cool running water or in the fridge) then you can cook it tomorrow without issues. You can refreeze it but I wouldn't suggest that, you will most likely end up with freezer burnt chicken that way.
If you left it out on the counter to thaw I wouldn't suggest eating it anyway…but usually there aren't problems, if you want to cook it tonight you can. However, don't save this chicken for later OR freeze it unless you want to get very sick.