Looks like ‘sprue’ excess solder from the joint above
Ah I see, thanks @Mr_Smyth. I was imagining something had for some reason sheared off. At least it shouldn't be anything to worry about then.
I'll live with it for the winter, it's not terrible, but equally not going back to the same person for its next service.
@Nayr started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
Nayr
Looks like ‘sprue’ excess solder from the joint above