ZBrushCentral

Zsketch to polymesh left some strange artifacts

Okay so I was messing with zbrush (for the first time so this is probably my error) I started messing with zspheres and zsketch and then made a polymesh, after some modeling around the head I go to the back and realise some odd edges and folds? over the back.
I made the pic smaller so not to be a loading nuisance but you can still see clearly what’s wrong.

sharp.jpg
EDIT: thank you Mod for the heads up on image hosting

any Ideas on what went wrong or how to fix?

Thank you in advanced,
Bombshell