Hi Saritha, 

As far as I have read and according to our sources, you do not have to worry about the details of your son's first attempt in January. It is only handy when you will compare the final results but certainly not for re-registering for the April session. 

Consider this as a completely separate, fresh exam, hence, your registration process will also begin anew. However, if in any case there are any changes or if you have to register using your old details only, I shall let you know. 

Hope this information is useful to you, I will get back with you with the necessary soon, till then, kindly do not worry.