As you are not able to straighten your finger, the conditin that you have highly likely to be Dupuytren's contracture.
Dupuytren's contracture occurs when the connective tissue in the palm thickens. Often the tissue thickens in one small area first and a “nodule” forms (a small, hard lump about 0.5-1cm) under the skin of the palm. The nodule sometimes feels tender to begin with, but this usually passes.
The nodules are non-cancerous (benign) and the condition is not life-threatening for those who develop it, although it can be a nuisance to live with.
Over time, the nodules can extend and form cords of tissue. These cords can shorten (contract) and, if the cords run along a finger or thumb, they can pull it so it becomes bent towards the palm. These contractures are often mild and painless, but they can get steadily worse over time.
Sometimes, the term Dupuytren’s disease (palmar fibromatosis) is used instead of Dupuytren’s contracture, because not everyone with the condition will develop contractures.
Make an appointment to see your doctor to get the correct diagnosis.