It may be worth your effort to have it treated. A simple form of treatment using a splint may even work when the injury is quite old. Usually continuous splinting for six weeks followed by six weeks of nighttime splinting will result in satisfactory healing and allow the finger to extend.
The key is continuous splinting for six weeks. The splint holds the distal interphalangeal joint in full extension and allows the ends of the tendon to move as close together as possible. As healing occurs, scar formation repairs the tendon. If the splint is removed and the finger is allowed to bend, the process is disrupted and must start all over again. The splint must remain on at all times–even in the shower.