I would have the Dr. check it just to be on the safe side.
I have a lump on the back of my knee that will swell up to the size of a small egg if I am on my feet a lot, etc and hurt. Turns out it is a baker's cyst and best to leave it alone, per the Dr. The scarring to remove or drain would not be worth it because it is the end result of some type of knee injury and would probably re-appear. I have some lidocaine patches that I will put on it when it is really bad.
Just check it and monitor it regularly.
PS. Leanne is right..... I totally forgot about a limpoma (sp) I had about the size of a walnut right where my low rise jeans hit. No pain but you could see it. I opted to remove it last June. Dr Russell Sparenger took it out. I did not want to go to outpatient and he did it in his office with local and my Hubby right there watching. Tmi but it looked like he was picking some fat ( like you see on chicken before you prepare it) out. You can not see the scar hardley at all thanks to vitamin e oil.