I Felt A Sharp Pain In My Arm About Fours

I felt a sharp pain in my arm about fours weeks ago and it left me with nagging pain. Then a week ago, I went to the ER for acute bursitis. May or may not be related. The arm has felt achy though the bursitis seems to gone. But now there is a big bruise forming down my arm but mostly at my elbow. What is going on?