Okay.. scans are finicky.. they only pick up a cancer that is a certain size. MICROSCOPIC CANCER IS NOT PICKED UP ON A SCAN. If you had a node pop up then there may be a primary somewhere else ( a few people have had an occult primary - but often they are later discovered elsewhere. If you are complaining about tongue pain. I would wonder if perhaps you have something going on there and it has spread to the node. Even superficial t1 tongue tumors can spread to a node if they are aggressive. (A tongue tumor doesn't have to present as a lesion or sore either - sometimes they grow inside the tongue as a tumor - palpating the area will tell you if there is potentially something going on there.)
Are you at a CCC? I would advise getting a second opinion at one if you aren't. This cancer can be tricky. It's best to have an ENT very experienced in Oral cancer.

A neck dissection is not a hard surgery, but it would be helpful to be certain that there isn't a primary hiding somewhere, before you go in and have to have another surgery after the fact.

hugs and best of luck.