Police are appealing for information after the 20-year-old was punched in the face.
At 4.10am on Saturday, May 18, the woman was walking along North Road with friends when she was approached from behind by two other women and hit in the face by one of them.
The women then walked off in the direction of Cable Street and were overheard making a racist comment.
The women are described as having blonde hair and one was wearing a pink top.
PC Faye Tinker said: “Thankfully, the victim wasn’t seriously hurt; however this was a very upsetting and unpleasant experience for her.
“If anybody was in the area at the time and has any information about this incident they are asked to call police.”
Anybody with any information can contact police on 101 or Crimestoppers anonymously on 0800 555 111 or on-line at Crimestoppers-uk.org.
You can now receive free crime alerts and advice at www.lancashire.police.uk/intheknow.