LLC, Personal Checks, Don't Pierce the Veil!

I buy and sell merchandise online. When I sell to buyers, they make their checks out to me personally.

I formed an LLC today (today is the Effective Formation Date) and I notified all my buyers to begin making their checks to me payable to my LLC (instead of me personally).

However, what is the proper thing to do with those checks my buyers *already* wrote a couple weeks ago (that are currently in the mail on their way to me) that have been endorsed to me personally? 

In other words, over the next couple weeks or so, however long it takes for mail to be delivered to me, I'll be receiving checks made out to me personally, daily.