Yes according to the Mayo clinic you can get Shingles without a rash. It is more common to get it with the rash but it is possible to not have a rash..
You can have shingles without a rash, but you may have something else going on and it's good you are having the MRI done to rule other stuff out. Best wishes.
I too understand that you can pain and no rash with shingles. As you probably already know, shingles attacks the nerve ends, hence the pain.
Another cause for underlying skin pain is from an infection in the deeper layers of the skin called Cellulitis. You can get this anywhere and it can happen if you get a cut or a puncture anywhere on your body (even through broken eczema) that bacteria can enter through.
Lets hope you get some answers from the MRI.
Best of luck.