Can I use a smaller lawnmower blade?

Okay, a while back I hit a log while mowing and blade began making metal on metal sound. I quickly replaced blade but for whatever reason the new blade began hitting the underside and getting hung up and not being able to move while I mowed. I literaly took a hammer to it and began hitting the undersides of the mower with my hammer. Problem solved for several mows. However, today, the problem returned and I did the same thing. Hammered the insides of the mower and once again no problems. This is a craftsman 22" blade mower. Can I just save myself alot of grief and switch to their next lowest inch blade like their 20" or 21"? Please help..thanks