Suggest Remedies For A Dark Mole Development On My Back

Hi I have an irregular and recent mole upon my back. It is soft yet has a much darker colouring to moles I have seen on others. We have no family history and I am otherwise mole-free. I am aware that this could require a biopsy, but am struggling to find a walk-in clinic in london on a Saturday. Are there any other things I should do or check by self-exam? I suppose I can wait until Monday? And I have developed severe muscular back pain in the spinal area and am worried there may be a connection, thanks for your response.