Swollen glands/lymph nodes

About three weeks ago I noticed that the gland and lymph nodes in the right side of my neck had swollen up. I just figured oh I’m about to get sick, they’ll go down. But it’s been at least three weeks now and I haven’t been sick or even had a slightly sore throat and they’re still swollen! Has anyone had anything like this happen to them? Or have any advice on what it could be?