What Does Numbness On The Thumb Indicate?

Yesterday while sitting in the car (not driving) I noticed numbness in my thumb. When I looked at my thumb, it was discolored light purple to the distal joint on the palm side, but not on the dorsal aspect. The thumb was a bit swollen, the joint was tender and stiff. I could not think of any trauma to the area. When I got home and looked up these symptoms, it sounded like this is something that happens and that those who had full work-ups found nothing that would have caused the problem. One paper said that full work up should be avoided. Today, the bruising has progressed to the proximal joint and is also present on the top aspect of my thumb. I have a good radial pulse. I am female, 64 years old, never smoker and in good health. I do have some osteoarthritis in some of the joints of my fingers.