Police say the man became aggressive inside Tasty Wok, in Parkfield Road, Parkfield.
He is said to have grabbed the woman before twisting her arm at around 6.30pm on October 12.
Officers have now released an image of a man they want to speak to in connection with the assault and are appealing for the public's help in tracking him down.
A West Midlands Police spokesperson said: "We believe he became aggressive to the woman before grabbing and twisting her arm."
Anyone who recognises the man is asked to call police on 101 or contact Crimestoppers anonymously on 0800 555 111 quoting crime number 20WV/235204H/18.