Melamine coated board problem.

You can get 20mm or 30mm edging - perhaps look for worktop edging. In my very limited experience cutting oversize edging can be a PITA but I possibly used wrong method just using a craft type blade (in a handle)

Re-wet the edge of the board with some 50:50 water:pva and then firmly clamp the edge (with lots of clamps) between two flat planks to flatten back the swelled edge. You may also find tat once the weetabix has swelled up a bit that it need to be sealed with a bit of PVA before applying iron on edging.

Possibly use oil based paint to cover any very small gaps. Apply and then wipe off from the face of the melamine immediately. Possibly don't try and make good with one application - wait for the first coat to dry before applying the next.

There are special tools for the job, although I have never used one myself. Just as an example:

get a larger width of banding tape, then use either a flush trim router, or one of the "stanley blade" type of laminate trimmer/cutter.

Cut-off the damaged section and glue a piece of hardwood trim on the edges to get it back to the size you need. If necessary, then either use a laminate trimmer to get the top/bottom levels correct, or very careful planing with a sharp block plane.

No, they are now going to go on either delaminating if plywood or swelling if something else. I have a bathroom vanity unit that is going this way since a tiny leak in a hot water pipe several years back.

Surely, they should have been skin wrapped in that saran wrap everyone uses. Brian

I would trim off the swollen edge or you may have perpetual problems

I wold avoid the Stanly blade type edge trimmers as they are prone to snag. The best tool is a blunt plane blade, or chisel blade. Yes, blunt. Held at the right angle it will glide along the dge with ease

Good advice! Once chipboard gets wet and swells up, you can't rescue it.

For tripping the edges, I use this type of thing:

I bet most of us have experience of that. Best solution is to go back in time & buy something that isn't complete crp. Next best option: fit a wooden lip after trimming off the damage. Bodgy option: fit wider edging tape, trim to fit. It'll never look right.