Pawan Kumar said that he had wanted to vote for the Bahujan Samaj Party in the second round of the election in the northern state of Uttar Pradesh.
But instead of pressing the button for the BSP’s elephant, he pressed the button with the lotus, the symbol for the ruling Hindu nationalist Bharatiya Janata Party.
Mr Kumar told the ANI news agency: “I accidentally pressed the button having the lotus symbol instead of an elephant.
“I chopped my finger for the mistake.”
Symbols are used beside the names of candidates so that Indians who cannot read are still able to vote.
As a dalit (formerly known as “untouchables”), the election is one of the few times that the 25-year-old gets a chance to have his say.
According to India Today, he had been “frustrated after the error and could not control his emotions” after his mistake.
He was taken to hospital but was well enough to return home later.
The BJP is tipped to come out on top after the election with the main opposition Congress Party expected to fall short, despite wrestling three major farming states from the BJP in December.
Some 900 million Indians are eligible to vote, making India’s election the largest in the world.
Voting takes place over seven stages and initial results are expected on 23 May.