I've gotten bitten on my finger while babysitting and lost feeling in my left thumb and nail it has been numb for a week now and today I started to get a burning feeling by my thumb I don't have medical nor money to pay to see the doctor what can be the c

Digital nerve . The bite may have injured the digital nerve that supplies sensation to that area. I would sure be seen about it as that is an important area with need for protective sensation and function.
There . There is very little description here. Don't know if this is a human bite or an animal bite. Cat bites are notorious for getting infected. I will make the assumption that you were bitten some where near the thumb nail? Don't know if there is redness, swelling, broken skin, bruising, warmth. Don't know if the numbness involves the whole thumb. Don't know if your symptoms are becomig progressively worse. I will assume the worst case scenario for the sake of safety. If you do have an infection it can spread upward toward the hand. I know you said that you don't have medical insurance or money. Because you live in an area the size of fresno, california you should be able to look up on line for free and sliding fee medical facilities. With the pauce information provided, would recommed that you get medically evaluated.