Done mistake while applying for SBI clerk form

It is a mistake on your part. We should fill the forms with more care. These are very important things and should not be taken so casually.

What I can suggest at this juncture is that you inform this to them through an application as well as email giving all the details and mentioning that it was an inadvertent mistake on your part and was not intentional. Please send this application by registered /acknowledgement mode and keep the receipt of the registry and acknowledgement (when you receive it back from them) with you. Now keep a copy of this application along with the acknowledgement with you and present it at the time of the document verification so that if they say they have not received it and no correction is done in your personal data then you can request them to consider it at that point of time.

You must have applied through IBPS combined bank clerks exam. So go to their site and under the menu 'contact us' find out their address and phone number so that you can send your application to them at that address as well as talk to them on phone for any doubt or query in your mind in this matter.

You should have taken step while sending the forms to the concerned officials.
At this juncture, you need to send them a request incorporating the mistake, you have committed showing your due apology for such a mistake.
The letter is to be sent to the appropriate authority in a registered post with an acknowledgment- receipt to be tagged with the envelop containing your application and finally the acknowledgment- receipt would reach to you once they receive the letter.
This receipt is to be kept as a proof of your initiative and may be shown during the process of document - verification.

One should be very careful while filling the applications. Small mistakes will result in a big way. Anyhow, the only way now you have is to contact the concerned authorities and inform them about the mistake and give them in writing saying that it is a mistake and not intentional. You can attach your marriage certificate also. If you are not able to reach them directly you can send an email or a letter by registered post with acknowledgement due. Keep copies of all the correspondence papers for reference. They may not disqualify you for this reason as it is not related to your age or educational qualification which are very important.
Another option is to take the risk and keep silent. Once you get a job and asked you to come for verification of documents, you can carry your marriage certificate and tell them about the mistake if they ask anything related to that.
In my opinion, it is always better to contact them and inform them in advance is the best option.

It is ideal not to commit any mistake. The mistake would ave happened due to hurry or lack of expertise in online filling.
As of now it need not be taken as very serious and worried about. Your selection is not going to be based on this particular parameter.

The matter may be coming up in the interview when they ask or confirm your bio-data. If it comes up, then you can correct the data there and admit that it was an inadvertent mistake and you want it to be corrected.

If the matter does not come up in interview also, then you need not rake it up. Wait until you are selected.
When you are appointed the concerned bank takes a fresh set of forms on your bio-data. At that time be more careful and fill up the correct details.

As of now do not worry unnecessarily on this mistake. Focus on preparing for the relevant test and/or interview. Best Wishes.