My dog has a lump under his neck

Hi everyone, my Labrador has had a large lump under his neck since this afternoon. We've checked him over and the lump is quite hard and big. I really don't think it's hurting him as he's acting just like his normal self. Some friends of ours had a look and said he's probably swallowed a wasp or something that stings (they know their stuff when it comes to animals). I'd love some advice as I'm getting a bit stressed about it 😞 hoping for a reply as soon as possible.

Regards

✌

See you soon... 👋