Could it be a swollen lymph node? Does it kinda "squirt" away when you push on it? The size of a grape sound big for one of those, but it might be. Those will swell when your body is fighting off an infection, and even if you haven't been sick you may have been exposed to something and your body fought it off. Anyway, they do tend to stay enlarged for awhile afterwards, so it's not unusual to have one swell for a few weeks at a time. DD had one in her neck for AGES, and the pediatrician kept checking it and saying that as long as it moved when you pushed on it, it was fine.
me , he , my three , , and -- and the one we lost