The student, a native of Batlagundu in Dindigul district, has been hospitalised, they said.
The student had allegedly posted a comment on the site on one of the photos uploaded by the lecturer on Monday. Hurt by the comment, she informed her husband who lodged a police complaint yesterday.
Police summoned the student, questioned him and told him to apologise to the lecturer. He was then sent back.
He was rushed to the General Hospital here by his classmates and is being treated, police said.