A bottle containing an “accelerant” as described by the West Midlands Police was thrown into Kashmir Meat and Poultry shop on Wednesbury Road in Walsall whilst a worker was still inside at about 5.25pm on Monday 27 June.
It collided with the victim, causing bruising but no serious injury.
Fire damage was also caused to the shop causing it to burst into flames.
Zahid Akhtar, who was on the scene soon after the attack, said: “The area was cordoned off and the shop was surrounded by police officers.
“There were also a lot of police cars and fire engines there.
“Luckily I don’t think anyone was seriously hurt.”
The attacker was described as white, 6ft tall and wearing a blue jacket.
West Midlands Police is investigating the attack by examining CCTV footage and going door-to-door in the area to pose questions to the public.
Local officers will also be seen in the community, carrying out reassurance patrols.
The force could not instantly deem the act as a hate crime.
Det Insp Greg Evans, of West Midlands Police, said: “The inquiry is at an early stage and I am keeping an open mind as to the motive.
“The man was not seriously injured, but it could have been much more serious.”
Anyone with information should call police on 101 or Crimestoppers, in confidence, on 0800 555 111.