In 1986, as a child actor, Pinnock starred in the fantasy drama TV serial Mr Magus is Waiting for You, based on the novel by Gene Kemp and following the adventures of four young children who get mixed up with a mysterious Magician. He then went on to play guest roles in television programmes like Grange Hill, EastEnders, The Bill, Dalziel and Pascoe, Footballers' Wives and Casualty, to name but a few. TV movies followed such as Kingdom of The Blind with Clive Owen and Diamonds with James Purefoy. Theatre work included As You Like It at Stafford Castle at the Staffordshire Shakespeare Festival, followed by working with Directors like Kathy Burke in Hampstead Theatre's production of Born Bad and David Grieg and Marisa Zanotti in the Edinburgh Festival official production of the critically acclaimed San Diego and most recently Topdog/Underdog in Glasgow's Citizens Theatre.

Pinnock appeared in his first Hollywood feature film, the 2011 summer blockbuster Captain America: The First Avenger, as a SHIELD Tech. That same year, he went on to play the role of Leon in a four-part award-winning drama Top Boy, which was broadcast on Channel 4 over four consecutive nights from 31 October 2011. After the 2011 England riots in London, Pinnock appeared in the BBC docudrama The Riots: In Their Own Words, The Rioters. The following year, Pinnock portrayed the role of Evan in the ITV drama The Ice Cream Girls. The 3-part drama aired in April 2013.

Pinnock portrayed a young Nelson Mandela in the ITV docudrama Mandela: The Prison Years, which aired on 15 December 2013, the day Mandela was buried. Directed by Emmy and BAFTA award-winning Director Tom Roberts, the programme charts Mandela's sentencing in 1963, his arrival at Robben Island through to his release on 11 February 1990.

In 2015 Pinnock showcased the role of Frank Sutter in Fortitude on Sky Atlantic. He went on to play Jay 'The Sport' Jackson at the Bush Theatre in London, starring in The Royale. The play opened to rave reviews in November 2015.