Despite the small size of a finger infection, the medical consequences can be extreme. Anyone presenting with a red, tender or painful, swollen finger following trauma should be evaluated carefully. Treatment may begin with nonoperative care but must be quickly replaced with surgery if results are not seen within the first 24 to 48 hours.
Since you are receiving hand therapy and having trouble straightening your finger, it sounds like you may have been initially treated for a flexor tendon sheath infection. Complications are always a possibility after any traumatic injury but especially after one that leads to a flexor tendon sheath infection.
Adhesions, joint capsular thickening, and destruction of the tendon pulley system by the infection can leave you with a permanently stiff finger. Even without the more serious complications, up to one-fourth of all patients with flexor tendon sheath infections lose their ability to straighten the affected finger.
Hand therapy to maximize finger motion is a good idea. Even with therapy and carrying out your home program every day faithfully, there is still a chance you might not regain your full finger motion. Studies show that anyone with diabetes is at increased risk for this type of infection and possibly a less than favorable result. Other risk factors include age over 43, kidney or peripheral vascular disease, loss of blood supply to the area, and multiple bacteria present at the same time.