Lump on inside of ankle

I have a small lump on the inside of my ankle / foot, below the ankle bone.
It is more prominent when I weight bear.
I think it’s been there for a while, but now it’s painful and the area around it is painful.
I’m not aware of any recent trauma that set it off.
I was in an ankle brace for about six months last year for posterior tibial tendonitis caused by repeatedly turning my foot over – I have Ehlers-Danlos syndrome.
Why should this lump suddenly have started causing problems?
It’s not that big, just sore.