Normally it's just artifacts of display used by Moi for speedy display!
(menu Option / Meshing Parameter )
If you export your model and render it you will see that is not existing! ;)

But in your case seems it's really a problem of geometry at the top :)
During the process of drawing one of your curve control points is too large!



artifact anywhere due the dispaly speed!;)


<< 2. The rounding could be a little softer
Just around more your drawing of curve!:)