I slept on my thumb and now I'm not sure what's going on?

Okay so one morning sometime last week (it might have been Wednesday), I think I had slept on my thumb because I woke up and it was red and it felt like the circulation was bad. I thought it would go away on its own, and it slowly has, but it still isn't back to normal. And strangely, it is only happening on the left half of my right thumb. As I said, it is almost better, but I am not really sure what happened to it. Did I somehow damage a nerve or something? It doesn't cause me pain or anything, I'm just asking this out of my own curiousity.