This morning as I placed my hand on the steering wheel of my car, I noticed my wrist was very tender. Looking at it, there was what I believe was a vein significantly swollen. I had to drive my children to school, and in the 15 min that took - the swelling went down and bruising discoloration began to appear. No physical trauma occurred, no bite or sting. The area is very tender and warm to the touch. My hand and fingers were cold and had a tingling sensation. What could have caused this?