Why do I have tender swollen lymph nodes in my neck since yesterday?

Infection? You probably have some form of upper respiratory tract infection, likely viral. Lymph nodes help fight this and enlarge and are tender in the process. Hope you are better soon.
Monitoring Centers. Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells and digested food. Lymph nodes "taste" the lymph for anything bad like bacteria, viruses, cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.

Related Questions

I've had swollen lymph nodes all my life on my neck. I get sick a lot, and sometimes the lymph nodes feel tender and bigger.

Hematologist. It is not feasible to provide a meaningful opinion without examining you and your symptoms warrant evaluation by a physician. It would be preferable to consult a hematologist for an evaluation. Read more...

It been a week my neck is sore underneath chin my doctor told me no swollen lymph nodes why can it be?

Gland. You may have a blockage of a gland that helps with saliva. One option for treat that is sialogogues (saliva inducers) such as sour balls. That may help expel a blocking stone. Consider also continuing md follow up to look at other possibilities if it doesn't improve. Read more...

I have had swollen lymph nodes in my neck for over 9 months. Now when I drink they swell more and hurt. What could this be?

See a doctor please. Anything that lasts that long needs to have an evaluation and recommendations for care. I would strongly suggest you make an appointment with a physician asap to rule out any significant problems that could possibly be taken care of easier early then later. Read more...
See a doctor. Persistent lymph node swelling associated with other symptoms can be serious. The peculiar symptoms that occur with drinking could be hodgkin lymphoma. Other less serious causes could be the reason, but given what you describe you need to see a physician. The prognosis for hl is usually excellent but you need to get this taken care of. Read more...