The man was dressed in just a pair of jeans and a striped dressing gown, with a naked chest, Humberside Police said.
A member of the public contacted the force shortly after 7am on Tuesday, and said he had been approached by a man in the Corporation Road area who was asking for help.
A police spokesman said he man had blood on him and was described as staggering along. The man was thought to be aged in his 30s, medium build, 5ft 10ins tall and was carrying a wad of cash in his hands.
He was later seen close to the Railway Street footbridge, and police officers searched the area around Railway Street, Freeman Street and Cleethorpe Road but the man was not located.
Despite extensive enquiries the identity of the injured man remains unknown and officers are keen to trace him due to concern for his safety given the described injuries and blood loss.
Anyone who can assist police in identifying the man is asked to contact police on 101 referring to log 72 of 20 October 2015.