I can't say I've had the lumps. However, the seemingly random joint pain yes!
I had my mirena for 5 years, and upon removal I suddenly had right hip and knee pain, as well as left knuckle pain in ONE knuckle. It's lasted months.
The most distressing symptom i've had is constant right sided chest/back pain. Count yourself severely lucky. I've had the chest pain for the 4 months since removal with no relief in sight. It seems to feel like a type of musculoskeletal joint issue, except in the ribs. Before anyone asks, it's not costochondritis. I've been through the gamete of tests, with doctors shrugging their shoulders.
I'm going on my 5th month post removal. I've been through 3 periods since removal. Each time my symptoms seem to lessen. As i've read on this forum it seems only time will tell.