After following every line of enquiry officers believe a social media appeal may prompt more people to come forward with information about the incident on High Street, Metheringham in the early hours of Sunday August 8.
They are hoping to hear from witnesses or people who might know something about the incident or the offender.
A spokesman said: “The victim was assaulted at around 1am during an altercation involving a number of people. The victim has suffered bruising to his left eye and a broken eye socket.
“If you saw anything, have footage of the incident, or know something about it, please contact us. No matter how small the detail you have, we would like to hear it.”
You can call 101 or email [email protected] quoting crime number 21000444932.
You can also contact anonymously via the independent charity Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.