The header has to come out and go back in from the other side. That is a fiddly job rather than an impossible one, and plenty of people get through it with the right tool.
You will want desoldering braid or a solder sucker. Working the header loose with a soldering iron alone is what tears pads off the board.
Heat one pin at a time and draw the old solder away with the braid or the sucker, until every pin on that header is clear of solder.
Check each pin moves freely in its hole before you pull. If one is still anchored, go back to it — rocking the header out while any solder is holding it is what lifts the pads.
Ease the header out, clear the holes, push it through from the correct side and solder it again. Tack the first and last pin first so the header cannot shift, then do the rest.
If you get stuck at any point — no braid or solder sucker to hand, a pad already come away, or it simply is not coming loose — stop there and message us here, or email [email protected], with your order number and clear photos of both sides of the board. Our support team will tell you whether it can be repaired. If a replacement part is the answer, damage that happens during assembly is charged rather than free, and we will quote you the price before anything is sent.