ok so I went to the docs yesterday to ask his advice. He did loads of little stretch tests on it, making me grip, bend, push and all that malarky. He then said
"Right, it's one of two things. Either a broken scaphoid bone, which is hidden right in there, or you've sprained the tendons in your wrist and they're now badly bruised. This test will find out which it is. I'll warn you, if it's broken or fractured, you're going to feel a little bit of pain. Well, a lot. It'll really hurt"
He then did the test wwaswas described up there ^, but with a bit more accuracy and a lot more pressure. And it was ok.
Pulled and sprained the tendons of my wrist, all badly bruised, but touch wood, no break.
Glad I got it checked – thanks for all your input everyone!