Swollen Lymph Nodes on my dogs neck

My dog is overall a very healthy dog. Aside from every blue moon having diarrhea or vomiting. The other day I noticed his lymph nodes by his neck were a little swollen. I didn’t think much of it since I know humans lymph nodes swell all the time and usually just go away. I was out of town for a few days and he was with me mom, and had no issues or tummy troubles. I just got home last night and he has had watery poop everywhere. His lymph nodes are still swollen and I am starting to get worried. I’m not sure if this is something that will pass and he just needs to be drinking extra fluids or if this is more urgent that I think it is. Please let me know!

– A worried dog mom.