Hard lump on left side of neck

I noticed a hen was lethargic, not eating or drinking or coming out of her coop. Her neck looked puffier than normal so I felt around and felt a hard lump or irregularity on the left side of her neck - not her chest. She tried to eat and drink a little out of my hand but she could not lower her head - only curl it slightly inwards and lower it just a bit. I did some research and saw lots of stuff about sour/impacted crop but it looks like that's all on the right side, she does sort of stink though so I gave her lots of water and turned her upside down but the only thing to come out was water and a bit of saliva looking stuff, nothing gross. I'm afraid she's hurt her actual neck and any massaging is just going to make it worse - we do have a dog, he has never bothered her before but he's been more unsupervised lately. There's been no blood, feathers, etc to suggest an injury though. Any ideas?