Ajala was born in Newham, London, and moved to Dublin aged five. He played youth football in Dublin for Home Farm, before returning to London aged 16.
Ajala began his senior career with Isthmian League side Ilford in 2008. He then played for Buntingford Town in the Herts Senior County League & former Bedfordshire League side Southill Alexander before going back to play for Danny Bailey at Middlesex County Football League side Interwood until 2011 when he had a trial with Doncaster Rovers before joining Championship club Hull City, though he never played for their first team. He returned to Interwood before playing in the Conference National for Hayes & Yeading United in the 2011–12 season. Ajala has also had trials with Brentford and Newcastle United.
Ajala joined Bristol City for the 2012–13 season, signing a contract until January 2013 then to the end of the 2012–13 season. He was awarded the number 35 shirt and made his professional début for the club on 16 April 2013 in a 0–1 home defeat to Birmingham City, a match in which City were also relegated. He came on as an 89th-minute substitute for Neil Kilkenny.
Ajala joined League Two side AFC Wimbledon on a short term loan deal in 2012. He made his debut for the Football League Two side in an FA Cup tie against Milton Keynes Dons on 2 December 2012. He made an assist for the equaliser but it proved only to be a consolation as the match ended 2–1 to MK Dons. He was recalled by Bristol City for upcoming matches.
Ajala signed for Welling United on 31 January 2014. He played 15 times for the Wings, before leaving at the end of the season.
Ajala signed a one-year deal with Torquay United on 20 July 2014.
On 9 September 2015, it was announced that Ajala had signed for Dover Athletic
On 4 January 2016, Ajala re-joined Torquay United, on a deal until the end of the season.
Ajala signed for Gateshead in June 2016 after turning down a new deal at Torquay.
Ajala joined Welling United for the second time in August 2017 and featured in the first half of the National League South 2017/18 opener versus Truro City.
Ajala signed for Dartford in August 2017 and made his debut versus Oxford City on August 19, 2017.