Born in Lewisham, Sid joined Millwall at just eight years old. Coming through the youth ranks, he signed professional terms in 2014.
He made his senior debut on 28th December 2014 and continued to develop in the squad for the next couple of years, making thirty-eight appearances in the Championship and League One. In January 2017, he made the first of multiple loan moves to clubs further down the pyramid, joining League Two Newport County until the end of the 2016-17 season.
He would be back in League Two the following year, first representing Yeovil Town between August 2017 and January 2018 before playing for Chesterfield until the end of the 2017-18 campaign.
In August 2018, he would return to League two for a third time, this time with Swindon Town, where he remained until January 2019, at which point he joined Tranmere on loan until the end of the season.
He arrived at Prenton Park with plenty of League Two experience, with well in excess of one hundred senior appearances.
Nelson played a crucial role in the latter stages of the campaign, making 10 appearances before the end of the campaign. He also played 115 minutes of Rovers' 2018-19 League Two play-off final victory over Newport County, as Tranmere were promoted to League One for the first time since 2014.
Following his release by Millwall, Sid joined Tranmere permanently, signing a 2-year deal on 26th June 2019.
Interesting Fact: Sid was the captain of the Millwall youth team.