low score on second attempt

If I'm understanding the situation correctly - it sounds to me like you submitted your application with the 510 score. After submitting you resat the GMAT and got a 580. Congratulations on a solid 70 point improvement. I don't know which school you applied to but most schools will accept additional information and test scores after you apply. I don't think you've blundered. You might just want to email the school again in a day and ask them for verification that they've received their new score.

sorry , If I wasn't clear . I scored 510 in the second attempt , and sent that score to the B school, using GMAT service just before writing the exam . My previous attempt was 580 ( so a decrease of 70 points). I had not selected any B schools at the time of taking the first attempt .

I submitted the application few days back mentioning my 1st attempt score (580) .Will the Schools get to see that score or only the second attempt score ? Also, is the score immediately available to them ?

I think it is going to make a huge impact , correct?

You should check with GMAC but my understanding is that when a school gets your latest score report - they see all the past scores. So the school will see both scores. They will use the highest score to evaluate your application. It happens somewhat frequently that a candidate gets a higher score on a first attempt than on a second attempt.