The victim was reportedly chased along Leyland Lane and into a "busy" Tesco Express by two men at around 11.30am on Friday, October 2).
He was then allegedly punched, dragged to the floor and stamped on near the till area.
Two men were later arrested on suspicion of affray four days later on Tuesday (October 6). They have since been bailed subject to conditions pending further enquiries.
A spokesman for Lancashire Police said: "We are dedicated to taking action against these violent individuals and keeping the streets safe. A further update will be given in due course."
If anyone has any further information about the attack, contact PC 273 Davies on 101.