Snowboarding, I landed hard on my chest, knocking out my wind. After a few minutes, I noticed that my right arm had little to no ability to move.

This was yesterday.

Now, I cant move my arm at the shoulder joint without significant pain, and I think it is impossible for me to lift my arm outward, as in shoulder flyes.

I can have other people move my arm around, as long as it is totally relaxed.

I am guessing rotator cuff injury. Could this be correct? And if so, what might be my prognosis?

Thanks in advance.