Hi @Rach78,
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
The main reason you are having issues is that your skirting boards are made of MDF, which is an engineered timber product that is like heavily compressed cardboard. It is very reactive to moisture, which, like cardboard, will cause it to swell and weaken.
If you were looking for a simple repair, then you could try sanding back the swelling sections with some 180 Grit Painted Sandpaper to smooth the surface and remove the swelling material, aiming to bring it back flush with the rest of the skirting board. I can't guarantee it will come up nicely, but it is certainly worth a try. After sanding, you would then prime and paint the skirting boards to match the surrounding surfaces.
Unfortunately, MDF is not the best material to sand, so it may not come up perfectly, in which case, your best option would be to replace the skirting boards with solid timber variants. Check out How To Remove Skirting Boards and How To Install Skirting Boards for some guidance on this process.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
