Fell three weeks ago landed on my arm, it was swollen a couple days and a little black and blue, arm still hurt arm does not hurt if at 90 degree angle but when i extend arm or bring in less than 90 degree angle arm hurt at front crease part of elbow

You : You could try simple measures such as over-the-counter medication, like Ibuprofen or aleve; however, it seems to me that it might be worth your while to seek additional input from your primary care physician. Three weeks is a rather lengthy time to have persistent loss of motion of the elbow.

Definitely : Definitely get it checked out. Problems with elbow extension after trauma to the elbow is common but could mean something that needs treatment i.E a radial head or neck fracture or variations thereof. You will need some good x-rays and possibly an MRI and/or ct scan. Even if there is no outright "pathology" you still want to see someone to get started with some therapy or you can end up with an unnecessarily stiff elbow. Good luck.