I'm an active 26 year-old male in otherwise good health, and the last couple days I've been waking up to a new fingertip being extremely sensitive. It started with my left thumb, which is very sensitive to any pressure now, as though I had bruised it. There is no visible injury, but by itself I had assumed I turned in my sleep and smacked my nightstand or something. When I woke up this morning, my left index finger has the same problem. To be clear, none of the joints are sensitive, and I can flex them without pain. Does anyone know what might be causing this?