Started to get pains in my middle finger it comes and goes and sometimes can last for a week at a time. it feels swollen and stiff. didn't damage it.

Finger pain: Intermittent pain, stiffness & swelling of the finger is most commonly due to inflammation of the digital joints. Examples include osteoarthritis, rheumatoid arthritis as well as gout. Monoarticular involvement be due to various conditions such as connective tissue disease and certain infections. Dr. Examination, laboratory testing, x-ray, +/- musculoskeletal ultrasound often provides the answer.

Trigger finger?: If it is swollen along the palm in line with the finger, or you get occasional locking (unable to move the finger), it could be a trigger finger. Many times a cortisone shot can help.