I see that it says you registered a year ago, but for the sake of precaution, when did you begin to actually play? (I feel like it's necessary to ask because more often than not, there are people who register for websites such as this, but stay quite inactive and do nothing till a later point in time)
If you've been playing throughout the year, was there any long pause before this recent play that caused the pain?
If there was a long break, it may just be the fact your hand is in a bit of shock from the sudden stress and overall exercise it's being put through. In a more common real life example, say you're a runner. You practice quite often and get to a certain point where you're able to run for miles with no break. Suddenly, a tragedy happens causing you you to have to stop running. Well, a half a year later, you run again like there was never a break, and due to the fact your legs started to calm down before it, your legs begin to ache and go under major stress from not being used to this sort of pressure you're putting it under.
Now, that was merely a real life example. Clearly it can be used for many other circumstances.
However, at the same time, I have to wonder: Was there never a break before today? Have you been playing constantly every day leading up to this event? If so, I'll continue with this if you say that is the problem.