Can you get arrested for this? England

Essentially a very odd dream inspired by recent events but nonetheless - if you are walking around a shop (Asda, in my dream) and somebody slaps your ass, in retaliation you smash an egg over their had that you had to hand. If they went to the police is there much that could be done? All on CCTV, proving the order of these events. Would anyone get in trouble? Is it self defence?