Pea sized lymph node swollen under chin right in the middle. is this more likely due to my sinus infection than anything really scary? (like cancer)

Cancer unlikely: Just monitor the node once a month or so. If it gets larger, i.e., twice it's current size. becomes painful or gets fixed to the surrounding tissue, see a doctor for evaluation. Otherwise you may watch and wait. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Probably not: Enlarged submental lymph nodes rare. They are involved only when a lesion is present in the anterior floor of mouth near the labial frenulum. If there is no lesion at that site, probably viral inflammation. Sinuses do not drain there. Should more lesions appear there, or there is significant enlargement then bx indicated. Most likely there will be resolution.