Good Afternoon A.:
My son also had enlarged lymph nodes pop up about that age. I also pointed them out at EVERY visit to my pediatrician. However, the pediatrician didnt seem very concerned so I didnt worry either. At about 2 he developed allergy shiners and the pediatrician just loaded him up on allergy drugs that didnt work.
At 4 they had changed those meds so many times and they continued to NOT work.
At six we were told they were due to his adenoids having issues so my son underwent a T&A this year. Guess what that didnt help either.
I finally gave up on our pediatrician although she is wonderful and the allergist was good. I took my son to Integrated Health Specialists at 93rd and Meridian and have found that the enlarged lymph nodes were due to MAJOR allergies and he is allergic to over 26 items (food and environmental).
I felt terrible as a mother as I didnt know. He is finally starting to improve but have to say, not thanks to his pediatrician or the initial allergist that came so HIGHLY recommended.
I share my experience not to alarm you but to just let you know that you need to watch his progress. If he has multiple sore throats/ear issues as he gets a bit older, it may be due to tonsils, adenoids or allergies so keep your pulse on it. Many kids have allergies to milk even as babies and that could also cause the enlarged lymph nodes. There are great products now like Soy Milk enriched with calcium etc...
You didnt mention what his eyes look like or if he has a lot of mucous in his nose, etc. Milk allergies can cause excessive mucous and allergies in general can give your baby a bit of those allergy shiners, dark circles, etc...