MeierEce,
To answer your question about symptoms. my daughter Heather had cancer in the base of her tongue. Her main symptoms were a sharp pain in her ear and a sore throat with a feeling that something was caught in her throat. She had no enlarged lymph nodes. A neck dissection revealed cancer in 4 nodes, but the largest was only about 1 cm.
Besides doing a visual with palpation, doing a scope like Brett said is a good idea. Depending on what that does or doesn't show, either a biopsy or a PET/CT scan would be preferable next. CT scans show some tumors, but not all (Heather's 3+ cm tumor wasn't detected). An MRI is better, but a PET/CT is usually better yet. Unfortunately, no diagnostic tool is foolproof.
The main thing is to have the doctor explain everything. If he thinks it isn't cancer, why not? If he says it's because you are too young or didn't use chew enough years, call him on it. Heather was 28 when diagnosed and never used any tobacco, but she died last October from oral cancer.
If the doctor has valid reasons for feeling the swollen nodes are no big deal, that's good, but make sure you are satisfied with his reasoning.
One thing you said leads me to believe that perhaps this is not cancer. You said that the initial swelling on the left side has gone down. Swelling doesn't usually subside once cancer is in a node.
Good luck and be sure to let us know the results. Hoping for good news for you.
Rainbows & hugs,
Rosie