Swollen Middle Finger. Tight Skin And Sore Mouth, Blistered. Who Can Help?

Hi, I have been to my family Doctor today with this but my problem seems to of mystified her.... I have a very swollen middle finger on my left hand - there are no bite marks or scratches and I know that I haven t damaged it - it is swollen from the main hand knuckle to the joint just before the finger tip. The joints themselves are not painful however it is painful to bend because of the swelling itself, the skin is so tight that it feels like it is going to split! Other symptoms that I have are; a very sore mouth, like it has been scolded and is blistered, my tongue has a very thick white coating which isn t normal for me and generally feeling off colour. The swelling started at about 7.30am this morning and I have watched it get bigger throughout the day, the sore mouth started about a day ago. I really hope that someone can help as I m in a reasonalble amount of pain.