What would cause the tip of my thumb to go numb?

It happened to me as a result of a slipped/bulging disc in spine, which apparently pinched a nerve. Even when the disc got better, the numbness persisted. You’d probably know if you had a slipped disc, though.

Some little girl recently told me that her aunt had developed carpal tunnel syndrome in her thumb from texting. I wondered if that could really happen so when I read your question I googled it and found this.
http://solomonsseal.wordpress.com/2010/02/12/healing-texting-thumb-and-repetitive-stress-injuries-rsi-with-solomon’s-seal/

My wife had numbness that started in the tips of her fingers in her right hand. Over the course of several months, it slowly spread to pretty much the whole hand. Shaking the hand would relieve it but only temporarily. Eventually, she went in for some tests (primarily a nerve conductivity test), and they said it was carpal tunnel. She had the surgery, and that took care of it. It’s back to normal now.

I get that in various fingers for a day or two at a time, but it always goes away in my case.

See, I work in a machine shop, so I do weird/bad things to my hands all the time, often without noticing. There has been many a time where my first clue that I have a cut is seeing red dots all over the place; some of the things that slice me are so sharp that I don’t even feel them cut. And sometimes I get a nerve that way and it’s a couple of days before I have full feeling in that finger/thumb again.

As you may have gathered, there are multiple possibilities.

@jerv Yes, thank you. I remember using a wrench to tighten a nut the day before, so that may be the cause. My thumb tip today is a little better, though I can still feel a bit of the numbness.

Thanks to everyone for your responses. You all were very helpful. :)