Could a chipped tooth fall out overnight ?

No: Are you asking if the tooth itself or the chip? It's extremely rare for a non-loose tooth to suddenly fall out. If the tooth is chipped and part of the chip is loose and attached by the gums, then it is possible for that part of the tooth to fall out. See a dentist to have the tooth evaluated and treated.

Big fear only!: One of the biggest fears patients have is if they loose a filling or a piece of tooth is: will the rest of the tooth come out. The answer is 98% of the time no! however, the remaining exposed piece of tooth may be sharp edged, allow food to impact, be sensitive to cold and be a deep area in the tooth for decay to quickly assault the nerve. See a dentist before future problems occur.