Mild shoulder pain, range of motion is just 20% with constant pain. Rotator cuff ?

I had small or mild shoulder pain in the past and my range of motion in the past was 90% to 95%, but 3 days ago pain started to be very pronounced and my range of motion is very small 20% with constant pain. I can lift my hand slowly with the other hand without much pain. However, if I try to lift left hand by itself I cannot do it because it is very painful. As a kid I did damage to shoulder I just cannot recall what kind. What do you suggest I do and do you think that these symptoms look more like rotator cuff or pinched nerve? Thank you.