I have severe burning sensation in my left shoulder blade, what could it be?

Varies: There are a lot of possibilities, I would encourage you to be seen for an accurate diagnosis. Among the more common causes are: spine related, such as a pinched nerve; peri scapular, such as a sub scapular bursitis; or even nonmusculoskeletal. A detailed exam and appropriate studies would likely reveal the problem and based upon that appropriate alternatives discussed.