Change of name of my son's PPF account?

I have opened a PPF account for my younger son in year 1998. At that time, he was one year old. At that time I have opened the PPF account in his nick name. Now the PPF account is in his nick name and all other documents in his real name. Is it possible to change the name or do we need to close the account and open another in new name?

You have to submit any of the following documents for your son -
1. Any government document like birth certificate or
2. Guarantee on 20 rupee bond paper.
Plus your douments -
1. Any document, which shows your relationship with your son (birth certificate of son)
2. PAN etc.

1. Identity proof
2. Date of Birth Proof
3. Passport size photograph
4. Self Declaration that he is your son and his nick name and new name