I have elbow tendonitis, after working out my right elbow cannot straighten out it also clicks all the time, what?

Clicking elbow : can be a sign of arthritis or a loose body which is also due to arthritis or swelling in the joint which come from arthritis or other causes. Decreased motion after activity may imply swelling is occurring and when that happens volume of the joint left to stretch out is effectively decreased. Another way to think of it is that the swelling tissues getting in the wY. Ortho eval is needed.