Nice and cool are sometimes interchangeable I think. For example, when you comment a good thing you can use both, but according to your feeling, the meaning should be slightly different. Other than this, you will also use "Wow, that cool! " when your friend did something very very nice. Or you can just simply use "Nice!" to add a short comment on something is good.
I found it is quite difficult to explain it, but I hope that I helped u to understand a little better :)
Best,