My Pelikan M205 was leaking a little. It seemed to be right around the feed. It made this ring of ink in the cap. Could it be that the nib wasn't screwed in properly? Or something else?

probably a loose nib because there's no seam there otherwise (such as one would find on an MB 146) to cause a leak. I'd say clean it up thoroughly (I'm sure you have already) and make sure the nib is snug (don't over-tighten of course) and see how it goes. If there's a crack in the section, you would likely have stained fingers just from gripping the pen for a few minutes. After cleaning up, try writing for a while to see if any new stains show up on your fingers. If not, then you probably don't have a problem. I've had a loose nib before and it usually results in excess ink around the base and poor flow.