The man, named Pawan Kumar, said he wanted to vote for a regional party but was but was confused by the many symbols on the voting machine.
Disappointed with himself, Kumar chopped off his index finger. Every voter's index finger is marked with lasting ink after they cast their ballot.
"I wanted to vote for the elephant, but I voted for the flower by mistake," Kumar said. The elephant is the symbol of Bahushan Samaj Party (BSP), a regional party in Bulandshahr in Uttar Pradesh, which has allied with other heavyweights against the BJP.
Mr Kumar is a Dalit (formerly known as untouchables) - a crucial vote bank for the BSP.
Party symbols play a big role in sub-continent elections because they are easy to identify in a country where literacy is low in many parts.
The Indian parliament, the Lok Sabha, has 543 elected seats and any party or coalition needs 272 MPs to form a government.
In 2014, BJP swept 282 seats which was regarded as a historical victory.
Polling started on April 11 and will continue for six weeks. The votes will be counted in one day, on May 23.