The ruined solder pad is the bottom left corner of the SD card slot. Also I attempted to pre tint the solder pads since that was what I was taught to do when I was learning how to build my racer drones.
The 4 pads around the SD card reader are there to secure it, missing one shouldn’t cause any problems.
It’s generally not a great idea to tin more than one pad when working with surface mount components as it gets very awkward to deal with if you don’t have a reflow gun to reflow multiple pools of solder at once. It’s all round just easier to solder large parts like the SD card reader like normal without tinning first, solder one corner to get it attached and realign it as necessary then solder the opposite corner to keep it in place while you solder the rest of the pins.
If at all possible, use some solder wick to clean all the pads and re-apply some flux before you try again, both these things are very cheap and very handy to have for future projects, you should be able to buy both at any hobby electronics store(if they sell solder and soldering irons, they’ll also have wick and flux).
@avarenity, did you make any progress? As @Tom and @Dalemaunder already said, this is really not a huge problem and the rest of the shielding pads will hold the SD holder in place quite nicely.