Hello, this is Dr. E. Greetings from New York! I'm so glad you posted your question for me to answer, and I aim to provide you with accurate info.
Skin darkening makes me worry about poor blood supply to the toes/foot (possibly due to infection like gangrene), so I do recommend you move up your appointment with the GP or go to the emergency department within the next day or two.
I have just looked again now, there are two little white 'lumps' also. Please advise.
The white lumps could represent pus pockets. Best to get it checked out in the next couple of days. You could need prescription antibiotics.