Heavily Discoloured, Bumpy sensitive skin on thumb? [photos]

I've had this for the last month thinking it was just eczema or something equally as minor, but it just won't go away... I'm now really worried as to what this might be. Any thoughts?

Edit: more context this has slowly spread from a small part on the top of my thumb to the basically half of my thumb. And now there are small hardly noticeable spots on both hands which I fear will grow into patches just like that on my thumb... The earliest I can get a GP appointment is in 12 days (which I've booked) so if any dr/dermatologist could give their opinion I would really appreciate it.