I have made a mistake in my cet form and submitted it and paid the fees as well. Will it be fine if i register again and submit the new form
Since you are confident that you have made a mistake in the form as well as paid the fees it would not be a good idea to apply again since it may overlap the current application.
The best thing you can do is to contact the official authorities for the correction of the application.
Glad to be of help, you can check this below link to confirm and get more details.
https://engineering.careers360.com/articles/kcet-application-form-correction
http://www.sarvgyan.com/articles