Pain in wrist could it be RSI?

I have a pain in my right hand and it travels down the inside of my wrist. If I clench my fist or hold a pen tightly the pain gets bad and goes on up my arm.

Yesterday evening I was stuck on a train for 3.75 hours and played games on my phone and ipod. I first got the pain when I woke this morning. Could it be RSI and what can I do to relieve/cure it?