Hello,

All the courses in NPTEL are free to enroll and watch so if you have enrolled for any course in NPTEL accidentally you are free to skip watching the lecture videos and enroll for any other course in which you are interested and watch the lecture videos. If you want to get NPTEL course certificate you need to register for the exam and score the minimum required marks by paying Rs. 1000 as exam fee. You have to complete weekly assignments and take the exam with minimum marks to obtain the certificate. If you do not wish to get certificate you do not have to register for the exam, you can just watch the lectures and complete the course.