I smashed my pointer finger yesterday on a rock and it is swelling and what can I do to stop the swelling?

You can try some ice, but ice is best within a few hours of the hit. Don’t put the ice directly on it. You can put some ice and some water in a ziploc bag and rest it on your finger so it is cold. Can you move it without increasing the pain? Are you sure it isn’t broken?

Probably a bad sprain and ice may help, but if swelling continues, see a doctor. It may be broken.

Is the nail discolored? Did you drive your finger straight into the rock jamming it or did the rock hit on top of the finger damaging it lengthwise?

When the swelling goes down and the pain lessens, pinch the finger. If it’s broken you will find a definite very sharp pain at the break site. It might be more efficient to see a doctor ASAP.