Yes... it is takes me 10 more days time to resolve this issue.

What is this issue? 

i could not open the Nintex workflow designer in the site ,when i try to open Nintex to edit the Workflow,Page will get crashed.

is it related to Nintex ?

yes.this Problem Related to Nintex,

What is the solution for this issue?

Finally i have found the Issue,it is related to Nintex threshold limit .if you have more then 100 list/Library in the Particular site,you will get this kind of Error,

Note:- this 100 list/Library Issue(AW,Snap),won't create any problem in Nintex performance, it will occur issue only on open the Workflow designer