The stone called 'Aamla' fell from the structure last night though no repair work was in progress, Deputy Superintendent of Archaeological Survey of India, J K Patnaik said.
The stone broke into pieces and a fragment hit the priest, Debi Prasad Panda, who was accompanying some pilgrims for 'darshan' of the deities, on the head, Deputy Supervisor of the temple administration Buxi Ramachandra Pratihari said.
The priest was taken to the district headquarters hospital and discharged after first aid, Pratihari said.
Patnaik said that he along with ASI engineer Sravan Kumar climbed the shrine today and verified the spot from where the stone had fallen.
Patnaik and other ASI officials were inquiring into the incident.
The ASI is in charge of conserving and maintaining the temple dedicated to Lord Krishna. The temple is greatly revered by devotees following the Vaishnava traditions.
