In the days leading up to the first on-set, did you expose your arm to any intense trauma? I once puncture the palm of my hand, the point striking one of the bones under my pointer finger. Doc said everything was ok, no nerve damage, no stitches needed, etc. About a week later I noticed that my finger tips were losing their strength, within 24 hours of noticing it, I had symptoms similar to you. It got to the point that I couldn't pick up a pen from the desk. I went to see an orthopedic surgeon and a neurologist and they both said the same thing: Deep tissue damage had caused inner bruising and swelling which put pressure on the nerves, inhibiting normal usage. It was very freaky, especially considering that I use my hands to earn my living. After a couple weeks, everything went back to normal.
A few years later when I dropped the bike and put a world of hurt on my hand, I experienced similar problems. I wasn't as worried about it and everything is fine now.
See the doc, think good thoughts and the best to you.