There are lots of places you can go for support if you have a concern. The important thing is that, even if you are unsure, you talk to someone and get advice:
Is there immediate danger or injury?
If yes – Contact the emergency services.
Report or seek advice on a sports related concern:
If the sport or activity has a National Governing Body, refer to their safeguarding procedures about who to report the concern to. See here for NGB contacts: www.sportengland.org/our-work/national-work/national-governing-bodies/sports-that-we-recognise
If there is no NGB or you cannot contact them, you can seek support from a number of sources:
Child Protection in Sport Unit (NSPCC): https://thecpsu.org.uk/
Active Essex: 03330 137827
Essex Social Care: 08456 037627
Report or seek advice on a non-sports related concern:
Contact Essex Social Care: 08456 037627
Essex safeguarding Children Board: 0345 603 7627 http://www.escb.co.uk/