Hello, now I think, there is two possibilities-- one is septic arthritis after elbow injection. but after Joint injection, chance of septic arthritis is low, if proper precaution has been taken Second possibility is related to trauma. But to reached to a conclusion, one need to see x ray and probably ultrasound of elbow, and above all, clinical exam by an expert Till you see your doctor again, I would like to advice that give rest to your elbow joint and avoid lifting heavy object from that arm. You can take pain killer as and when required.