What Causes Swelling And Inflammation In The Neck?

My neck is swollen..its directly under the chin right smack in the middle...Its a little tender and when i touch it, I can feel it. Not necessarily pain but if i touch it hard enough, yes pain... Its about a size of a golf ball and it seems like the inflammation is cover the adams apple. Its a bit uncomfortable when eating or just swallowing in general..What might be the issue? just inflamed, take some tylenol?? My friend accidently grabbed my neck the other day which *might* of caused it but probably not because that happened many times in the past and my neck never inflamed like this...