Hi - I think you should be in a good position where you are. Congratulations to a great score btw.
Did you have a strong quantitative component in your undergraduate degree? If so, that should probably suffice to show that you have good quantitative ability. If not, I'd recommend the trick that some users here have already posted in other threads: In your optional essay, simply state that you're willing to take additional math classes if required by the admissions committee.
Either way, I think a 770 clearly demonstrates that you are a strong candidate, and I'm sure admissions officers will think the same. So therefore, focus on enhancing other parts of your application - you've ticked the GMAT box!
Best regards
Steve