A man believed to be in his thirties was taken to Pilgrim Hospital for treatment after the incident on West Street.
Police were called to the incident at around 2.40 pm this (Saturday) afternoon.
The man has now been transferred to Queens medical centre in Nottingham.
It is unclear how injured the man is.
A man and a woman have been arrested in connection to the stabbing.
Boston and Skegness MP Matt Warman said in a statement that he had raised the "extremely concerning serious violent crimes" to the Home Secretary and the chief constable.
In the letters, he says he referred "specifically to nationality".
Last Saturday's shootings and Yesterday's stabbing have been connected to Eastern European migrants.
Police are appealing for any witnesses to come forward.