Honesty is usually the best policy. I suggest you report the oversight to your new school. Apologize profusely and hope they take pity.
That said, in my opinion:
If you chose not to report this I don't think there's any significant probability that you'd ever get "caught."
This NOT going to show up on a background check. Your school just wants a criminal background check run by computer. They don't hire a private investigator to snoop around, talk to your neighbors, and dig through your trash.
The Family Educational Rights and Privacy Act says that your community college can release information to your medical school without your consent, but the medical school would first have to ask every single community college in the country "Did Chris attend your school ever?" There's no way that every single community college in the country is checking their records to for each of the 20,000 medical students who are going to start school this year (plus the x-thousand dental students, y-thousand pharm students, z-thousand law students, etc. etc.).
It is true that you are required to be honest throughout your application. But the reason they're so intense with their cautionary statements is because they're never going to check.