The chief minister's tour across the state has often been marred by angry demonstrations by people, raising various demand, but the Tuesday incident is the first time that plastic chairs were flung at him.
A senior police official in Nawada said Nitish Kumar did not sustain any injuries.
The chief minister is touring the state addressing public rallies to mobilise support for the demand that the central government grant special status to Bihar so that it can access more development funds.
Despite unprecedented security during the Adhikar Yatra, it has witnessed angry protests from people on several occasions.
Para teachers, or teachers on contract with the state government, had held up black flags in some districts, demanding parity in pay and terms of employment with regular teachers.
After some such protests, the district administration in some districts, on instructions from the chief minister, banned people either wearing black or carrying black umbrellas, handkerchiefs and flags, from attending the public meetings.
Members of the Akhil Bharatiya Vidyarthi Parishad (ABVP), National Students Union of India (NSUI) and All India Students' Federation also staged protests against Nitish Kumar and showed him black flags in Begusarai, Khagaria, Darbhanga and other places.
ABVP is a frontal students organisation of the Rashtriya Swayamsevak Sangh and the NSUI is affiliated to the Congress.