First off, the cables on the stacking module (if stacking is configured correctly) wouldn't be a loop on your network. These are part of the Stacking Module which is/should be separate from your standard TCP/IP network. It may still be that the stack is misconfigured but that is not part of the question so we'll move on.
STP or any variant of STP (MSTP, RSTP...) is designed to keep loops from occurring on your network, as you already know. To go into a little more detail, enabling STP is recommended as it will help prevent someone from creating accidental network loops on your network and causing broadcast storms, which could bring the network down.
Being that you have the 6248 as the primary in the stack I'd assume you'd want to make it your root switch as well. On your 6248 under the STP configuration set the priority of that switch to 0 to make it the root. On the other switch you shouldn't have to change the value (unless it is configured as 0 already then just give it a higher value). By setting the 6248 as 0 this means it becomes the root of the spanning tree. If you leave the 6224P's STP priority as the default as this will not cause an issue. If the switch is not the root and is set to the default value then it calculates the priority based on the lowest MAC address value of the switches that are connected.
Here is a handy article that reviews some common mistakes when configuring STP. Hope this helps clarify some things. I would recommend keeping STP enabled and configured correctly to avoid any issues down the road. The protocol has very little overhead and reduces large headaches later...