I showed up at the airport this morning and while my student was pre-flighting I was talking to another instructor. He said the plane we were taking (c-172) did some "off roading" last night. A student pilot on a solo x/c somehow let the right wheel go off the taxiway into the mud. That caused the gear to stick and pulled the airplane to the right getting the nosewheel in the mud as well. I didn't get the story on how they got it out, but they washed it off and flew it back, no problems. After hearing that I did a really close inspection of the wheels and struts. I didn't see anything wrong so I decided to go on the flight. When my student landed we felt a strong vibration on the roll out. It felt like the vibrating came from the tail of the plane and felt similar to a plane that needs a new nosewheel dampner. Anyone think that maybe the strut bent going into the mud? I don't know what they did to get it out of the mud. I looked at the struts and wheels again after we landed and didn't see anything wrong.