I have a ton of these things. I used to think they were inflamed and knotted muscles, but my massage therapist tells me otherwise. I have a hard time telling which lumps are lipomas and which ones are myofascial trigger points, especially since most of them are in my back, so I'm not sure if any of mine are painful.
Humidity. The most common cause of condensation on double-glazed windows is humidity. The outside window is colder than the inside window causing fog or frost to build up in-between the two panes. The window and house is extremely airtight and cannot breath.
More than likely this may just be mildew from condensation and air infiltration. Mold and mildew develops on your window sills because the window frames are not thermally broken.This allows condensation to form on the inside of the frames during cold days and winter months. 1  The formation of condensation could be an indicator that your humidity level inside the home is too high.