Police are asking anyone who saw or knows about an assault and confrontation between a 14-year-old boy and a group of teenagers, to please come forward.
The victim reported being approached and assaulted at the park in Southwick Green at about 4.30pm on January 9.
Then he was approached again in Southwick Street, just south of the Manor Hall roundabout, at 4.30pm on January 10.
Police are appealing for people who were in those areas at the time to come forward, and have asked any witnesses to report it to officers.
Information can be reported to Sussex Police online or on 101 and quote reference 977 of 11/01.