Chilblains are an abnormal reaction of the small blood vessels in the skin to changes in temperature. The abnormal reaction results in a painful reddish itchy patch that then turns a darkish blue colour as waste products build up. The best treatment for chilblains is prevention.
The best way to deal with a chilblain on the toes is to keep the foot warm with socks and shoes and avoid as much exposure to cold as it possible. Rub a good cream into the chilblain to stimulate the circulation.
If these simple measures do not help, then it is probably a good idea to consult a podiatrist for further advice.