Hi, Jerry. Hate to tell you but it is the particle board swelling that is causing your problem. I don't know of a way to reduce the swelling but drying might let it shrink a little over time. It could also grow you a great crop of mildew if it has been wet for a long time.
The solution is not to buy particle board furniture. But don't feel too bad. I bought a particle board computer desk and ended up with a lap full of computer. I still have the desk but it now has real wood blocks at about every joint.