I wasn't exactly sure which area to post my problem under, so i came here, thought it was the closest. About 2 years ago while playing a soccer game, my left thumb got kicked and was broken at the base and about an inch up from the base. I was in a cast for about 1.5-2 months and had therapy afterwards to get it moving again. It felt back to normal within the year. It hasn't really bothered me since after that year until now. For the past couple of days its been twitching, not painfully, but it is irritating and bothering me quite a bit. I was wondering if anyone knew why all of a sudden it would be twitching? I haven't been overusing it, because it is my left thumb and i am right handed and i haven't injured it again in anyway.
My guess is that you are twitching in your thumb because your nerves were either bruised or damages in the injury. Nerves take months, even years to heal and while they do, the signals get a bit messed up along the way and start triggering involuntary movements. As your injury heals, i suspect your symptoms will subside.
Not sure about your situation, but I've been getting these "twitches" all over my entire body lately. Like you, there's no pain involved, but it is EXTREMELY annoying, especially when trying to sleep! On the net I've come across something called "Benign Fasciculation Syndrome." (But this apparenty is a diagnosis given to those for whom no obvious reason can be found for the fascics -- i.e., not MS, ALS, Parkinsons, etc. )