The striker climbed high to glance home the winner in the sixth minute of added time against Leeds at The Valley.
Jon had only entered the action as a substitute for Callum Harriott in the 86th minute.
"Jon has been chomping at the bit to play," said Charlton's manager Chris Powell. "And he certainly made an impact when he came on. I'm very pleased for him."
The win moved Charlton up to 12th in the Championship on 54 points - incredibly, there less than 10 points between Peterborough United in 23rd of 24 and Middlesbrough in ninth.
Staying in the Championship, Harry Kane came on in the 74th minute of Leicester's 1-1 draw at Brighton while Alex Pritchard was back on the bench after injury for Peterborough but an unused substitute in Posh's 2-2 draw at Huddersfield.
Adam Smith was also an unused substitute as Millwall drew 1-1 at Birmingham.
In League One, Massimo Luongo, Dean Parrett and Nathan Byrne were without a game for Swindon.
Unfortunately, Kevin Stewart didn't make the 16 as Crewe beat Southend 2-0 in the JPT Final at Wembley on Sunday.
Jonathan Miles was on the bench as Dagenham & Redbridge enjoyed a 1-0 win at Exeter in League Two.
In the Premier League, Danny Rose played 90 minutes in Paolo Di Canio's first game as Sunderland went ahead at Chelsea but lost out to two deflected goals in the second half at Stamford Bridge.
Andros Townsend looked lively as ever as QPR conceded a last-minute equaliser against Wigan at Loftus Road.
Away from the UK, Heurelho Gomes broke a bone in his hand in the 54th minute of Hoffenheim’s 3-0 win against Fortuna Dusseldorf in the Bundesliga on Friday night. The goalkeeper has undergone surgery and will be out for eight weeks. He will remain at Hoffenheim for his rehabilitation.
Yago Falque played 74 minutes as Almeria beat Recreativo Huelva 2-1 in the Segunda Division in Spain while Souleymane Coulibaly came off the bench in the second half as Grosseto lost 2-1 at Spezia in Italy's Serie B.
In the MLS, Jon Bostock played 73 minutes as Toronto FC came from 2-0 down to draw 2-2 at Dallas.