Forgot to file something on my taxes this year?

I have already filed my taxes for this year and just realized a major error.

My per the ITR, my taxable income is about Rs. 8 lakhs. But actually, it is about Rs. 8.8 lakhs.

Should I submit an amendment to my ITR, and how to do it? Is this a serious issue, and should I be concerned about this error?

BTW, I completed studies and started working last year, and this is the second time I’m filing my taxes.

How can i pay my credit card bill online if it is Mastercard??

Hellow, I am having ICICI Bank credit card. Which is visa powered card. So that i can pay my credit card bill by visa money transfer method by my ICICI Bank internet banking. I too have BOB Card which is Master card powered. How can i make payment for mastercard?? Which bank is providing facility to transfer fund to Master card like Visa Money transfer??