I believe I may have torn or strained something in my forearm. After playing a few hours of football over the weekend each day, Monday I was plenty sore.

I did some stretches and began doing some neutral pull ups. That's when handles protrude from the pull up bar perpendicularly. After three I felt a sharp pain and since then (2 days), the inside of my elbow is sensitive to the touch and it hurts to straighten my elbow.

I selected the area of pain here