If you still have the card then take it and I wouldn't say anything. They'll either look at it to verify it's the same or I've also seen Sri Lankan scan it through their reader on the desk and the PC verifies it. The check in agent in that case couldn't even see if I used Amex or Visa, so had to try a couple of cards before I got it right. Either way as long as you have the card you'll be fine.

If you've lost the card then you need to contact the airline as soon as possible.