Hey there! I just read your message. I wanted to ask, have you seen a doctor, preferably a surgeon about your medical problem? It's really hard to say what it is without investigating it. Maybe an Wikipedia reference-linkMRI and the examination form a specialist would help. It could be a cyst...which is not a big deal. Is it mobile if you try to move it, I mean if you place your fingers on it and try to rub it? In this 6 years hasn't it gone away at all ? Hmmm, I don't think it's anything serious really, maybe it's a benign formation, cyst etc. But I seriously recommend you get an MRI, consult and maybe run some blood test and check for infection. Hope it helps. Let me know how it goes.
All the best,
Catalina