I don't want to make light of the situation, but you also shouldn't worry excessively - after DD2 was born, I liked to lean against the headboard and read for stretches at night, but ours is made of wood slats (mission-style). Apparently I hit something just right and either irritated it and/or blocked flow of fluid, because that is how I got a smallish, sore knot in the same spot. I had no idea that there were lymph glands there, though, and went into a big panic (we've known more than one person with brain tumors).

I did get it checked out, and since I wasn't running a temp or anything, they didn't worry over much and it went away over a period of a few weeks - of course, I didn't read anymore after I got it (hurt to lean on it) and it took me awhile to connect the dots. At least you know that you have lymph glands there - you're ahead of where I was!

Do get checked out, but don't panic. I'll keep my fingers crossed for you...