Hi nook,
First off, congratulations on getting into your first-choice Program! There are some potential benefits to having a higher GMAT Score, even though you have already gotten into that Program - although you have to decide whether the extra time and efforts are worth it at this point. With a higher GMAT Score, you could potentially earn Scholarship money to pay for School - and certain industries/companies might be interested in your GMAT Score when you apply for jobs in the future. These issues might be best discussed with representatives of your School (and potentially through the School's Alumni network).
Do you have a specific reason why you're interested in retesting? if you choose to do so, then we should discuss your prior studies in more detail. If you would rather not discuss any of this here, then you can feel free to PM or email me directly.
GMAT assassins aren't born, they're made,
Rich
Contact Rich at: Rich.C@empowergmat.com