Police cordoned off Market Place and part of the High Street in the early hours of Saturday morning after a man was assaulted.
The assault on a 33-year-old man was reported at 4.48am. Police closed off an area of Grantham a short while later to allow officers to preserve evidence. It was reopened about two hours later.
A spokesman for Lincolnshire Police said: “The injuries to the man were not as serious as first thought and he was released after treatment at Grantham hospital.
“We would appeal for anyone who has information about the assault or was in the area at time to contact DC Brewster on 101 quoting incident 85 of 28 May. The independent charity Crimstoppers can also be contacted anonymously on 0800 555111.”