As per the Tamil Nadu Registration of Marriage Act, marriages solemnized under different personal laws must be registered. A marriage can be registered within 90 days without fine and within 90-150days with fine. After that it can't be registered. In the State of Tamil Nadu, three types of marriages can be registered – Hindu Marriage, Special Marriage and Christian Marriage. Since you are marrying a Christian, your marriage cannot be registered under the Hindu Marriage Act as it requires that both the spouses must be Hindu. A special marriage is one which is solemnized before the Registrar or solemnized by any local custom. In the possible scenario that you intend to register under this you will have to provide the proof of age of both bride and groom and a notice of the intended marriage by submitting the wedding card or such document. (http://www.tnreginet.net/english/spmar.asp) Your marriage will be registered if there is no objection received within 30 days.
Register as a Christian Marriage – Under Section 4 of the Indian Christian Marriage Act, 1872, a marriage can be solemnized as long as one of the spouses in Christian. Therefore your marriage can be covered under the Indian Christian Marriage Act. For the registration of Christian Marriage, you require a proof of age of the spouse and a proof that the marriage was solemnized. In a Christian wedding you will have to apply for Indian Christian Marriage Extract which is registered. (http://www.tnreginet.net/english/chmar.asp)
For the registration, you have to submit a proof that the marriage which can be a wedding invitation card or some other proof. In my opinion, if you submit the wedding card for the second day for the registration there will be no issue. In fact, your wedding solemnized by Hindu rites is not legally recognized as it is not covered by the Hindu Marriage Act. While your marriage by Christian ceremonies is valid and recognized by the Indian Christian Marriage Act and can be registered.