Ouch!

I have just pulled a weird little muscle in my hand attempting to manage a particularly big and difficult chord. It hurts. It also explains where that weird pain I had in my hand the other day came from. RSI, here I come! O Come O Come Emmanuel, go away!

So how does one exercise and stretch that muscle in the dip in the hand between back of hand and wrist? Should I be playing more studies? Should I put healing things on my hand? What? I have just deployed a tubi-grip... Should I just stop being stupid and over-ambitious (although I don't see how I can play this chord without being over-ambitious - my hands aren't very big)?

Humph. Not impressed.