If I cancel a check, does it impact my case?

I mailed a package to a NSC service center by EXPRESS MAIL (EMS) today, which includes a check. Now the package status is ENROUTE.

Now, I realise something I did wrong. I want hold this package back.

1. Can I hold it back? Does Express Mail have return, or similiar services?

2. If I cannot hold it back, I'll cancel this check. Does it impact to my immigration case? My I485 is pending in NSC.

Thanks, appreciate.