Conservation of ground beef
Per the FDA, you can hold the ground beef, refrigerated, for one to two days. 

Assuming you have:


Bought the meat from a reputable source (you seem to have if you watched them wrap it)
Have kept it well refrigerated since buying it, and will do so until cooking it


I would just cook and eat it as normal at dinner time tomorrow, since it has been refrigerated the entire time.  24 hours is not a magic number.  26 or 28 hours is not that different.  

Now, several days extra time before cooking would be a big difference compared to several hours.