What Causes Severe Elbow Pain When Moved?

Hi, my elbow has been hurting for two days and whenever i run, like when i do my arm movement to run (move my elbow and it bends up and down), im sure u know what i mean, its what everyone does when they run. but i want to know what the problem is and how i can heal. it hurts and i play soccer and i dnt wanna play soccer when i have one elbow hurting me.... i am 14 years old and im about 5'0 and weigh about 105