Yes, definitely, and at the earliest. Please do take this seriously. You are having Diabetes, and in all diabetics body immunity is low. The purple discoloration of the left foot 4th toe indicates infection, and possibly reduced blood supply to the foot. To prevent spread of infection and worsening of condition to gangrene of the toe, the most important you have to do is complete non-weight bearing of the left foot (Offloading). Please use a Walker and you may be ambulant in a limited way, using your right foot. It is possible that you would have to be admitted to hospital for intravenous antibiotics, blood sugar control and supportive management so that the infection of the toe would resolve and an amputation of the toe can be prevented. If the vascularity to the foot is low, the Podiatric surgeon would advise and peripheral angiogram and angioplasty or a peripheral bypass surgery to increase blood flow to the feet to help in healing if the infected toe and avoid proximal spread of infection.