Can rats chew through the wall? please help!?

They can, but they probably won't unless they think there is food there. They will probably leave on their own, but if you hear them again, you will need to call an exterminator or do something to get them out of there. They have been known to chew through wiring and insulation, neither of which is safe for you or your family. And it might not be rats. It could be squirrels or raccoons or cats or other nocturnal animals looking for shelter.