Hi Hayley
Welcome to the site.
Firstly, good luck with the MRI today. They're painless, just very noisy!
I would suggest that you read the posts on here and gather information from other peoples' experiences. We all know about ON and suffer from it daily, but each person is different. We don't all feel pain and symptoms in the same way.
Do you know what caused your tingling sensation/ON?
Mine was caused by a RTA.
As for how serious it can get.............it can get bad, but then again, we're all different. For some people it can be completely debilitating, stopping work, sleep and everyday activities. Fortunately I haven't been that bad.
Let us know how you get on after the MRI.