My elbow is very painful and in the crook of my arm a swelling has come up which looks like a swoolen muscle, Should I see a doctor or will it repair its self? I've had about four weeks.....
Firstly that is quite an unusual place to have a swelling.
Secondly, it is extremely unlikely that it is "life threatening"
At your age, it could be cyst, communicating with the elbow joint, in which case, should you be symptomless, needs no treatment. This cyst, filled with synovial (Joint) fluid is often associated with arthritis.
You GP will clearly make the definitive diagnosis.