What Causes Painless Lumps In Groin, Behind Ear And Under Armpit?

Hi, I have several hard painless lumps in my groin area at both side. I ve had these for about 3 years, recently I felt a pain in one but it lasted for about 24hrs then the pain went. I also has one under my left armpit and 1 really tiny one behind my left ear... what could be the causes for these? Should I be worried? I don t have any symptoms of fever, pain, or anything whatsoeve