It was a little out of season, but after several failed attempts modern medicine made a 6-year-old's Christmas wish come true. Nikea Warrick lost all her fingers in a 1983 house fire in Stratford, Conn. But surgery at Yale-New Haven Hospital has given her a new thumb that is now her "prized possession," said Alice Greene, the grandmother with whom Nikea lives. "She loves it," Greene said. "She kisses it all the time." A brief experiment three years ago with artificial fingers failed because they could not give the girl a sense of touch, Greene said. In August, 1986, two toes were transplanted to Nikea's hand as a thumb and finger, but they had to be removed because of a lack of circulation. Last December, said her grandfather, Thomas Greene, Nikea brought tears to a shopping mall Santa Claus with her request for one finger. In July, she had another operation. Dr. Stephen Ariyan, chief of plastic surgery for the hospital, headed the team that created her thumb. Ariyan took a bone chip from Nikea's hip, fused it to the thumb knuckle on her right hand, then cut a U-shaped flap in her abdomen, where he implanted the bone. The flap of skin then attached itself to the bone, while her arm was restrained until the healed thumb could be taken out. The first three times the procedure was tried, there were problems with the blood flow to the thumb and it was removed. But the fourth operation in August was a success. "She isn't used to it," Alice Greene said. "She's always banging it on something and saying, 'Oh, my thumb. I forgot.' "