Dhangar community leaders have launched an agitation for inclusion in scheduled tribes category and benefits of reservation.
Pune rural police said two persons were detained for interrogation after the incident.
Patil was treated at a hospital in nearby Baramati for pain in the left eye.
The incident took place when Patil stepped off the podium during the function and was accosted by protesters.
The minister, a Congress leader, later appealed to party workers who staged a protest in Indapur (his home constituency) to maintain peace and cooperate with police.
Patil said that the ink apparently contained some chemical which was causing pain and irritation in his left eye.
"I have always demanded justice for Dhangar community, and have been supporting it," he added.
He was advised to get admitted to a hospital here for further investigation to rule out major injury by the doctors who treated him at Baramati. He was on his way to Pune.
The Indapur-Baramati region has witnessed agitations by Dhangar community recently over the issue of reservation.
Meanwhile, a spokesperson of the Dhangar community said in a statement that the agitation was being carried out peacefully, and the workers should not resort to any unlawful acts.