If there is nothing functionally wrong (it’s not hindering charging) then there is nothing to fix. But like you have already been told…you are within the return/exchange period. Exchange it for a new one while you can. Beyond that time period your only option would be a warranty repair/replacement BUT if it is not having issues charging then it very likely won’t be repaired/replaced because it is not broken. Warranty repairs are for covered issues affecting functionality. The cord being wiggly but not affecting charging is not broken and does not mean that it will become a problem in the future. But if it concerns you even a little I would suggest taking advantage of the return/exchange period.
Not to mention…you don’t know if the port is loose or if the cable connector (on the cord) just has some wiggle room. You never said the port was loose (and if it actually is loose you would definitely have some charging issues occurring now). Point is…take advantage of the window to get a new device or your remedy if they need to repair it would be either a repair on your device or a replacement with a refurbished one regardless of how long you owned it. Say you owned it for 20 days and they need to replace it. You will get a refurbished one. That is stated in the warranty terms but a lot of people get upset thinking they should receive a brand new one