I have swollen fingers and can't make a fist what causes this?

Please go into MUCH more detail about yourself, and don't make us ask 20 questions.

It could be caused by any number of problems. A real-life doctor has to check your hand(s), blood pressure and other vitals, and maybe do blood work. No one, not even doctors, can diagnose on the Internet.

Let's see...

You are turning into a zombie
You were bitten by a bee and are having an allergic reaction
You hit your hand with a hammer
You closed your hand in a car door
You dropped a brick on your hand
An elephant stepped on your hand
You were doing a motorcycle stunt and flipped the bike and landed on your hand

Really, it could be anything...how are we to know? We need details and ultimately will probably tell you that you need to see a doctor.