At 19 years and 125 days old, Nelson has reached the tally 225 days younger than Brazil forward Firmino was when he did while on his way to netting 49 goals for the Germans before sealing a move to Liverpool.
It has taken just 19 games for Nelson to net seven goals for Julian Nagelsmann's team, who are sixth in the German top-flight and aiming to seal a place in next season's Europa League.
However, Sunday's strike brought an end to his 11-game goalless run, with his last goal for the team coming in November against Augsburg.
Nelson was exiled from the Hoffenheim squad for a brief period after turning up 20 minutes late for training one day, but has bounced back to maintain a place in the squad after accepting responsibility for his error.
“You can make mistakes but it’s your job and you shouldn’t be late," he said last month.
“I held my hand up and I said sorry to him and we both moved on as bigger men. He put me in the squad the next week because I’d been doing well.”
7 – At the age of 19 years and 125 days, @ReissNelson9 becomes the youngest @achtzehn99_en player to score 7 goals in the #Bundesliga , surpassing Roberto Firmino (19 years, 350 days). Youngster. #TSGBSC pic.twitter.com/8cpbTwxzRw— OptaFranz (@OptaFranz) April 14, 2019
Their combined 17 goals equals the Bundesliga record of goals scored by English players in a single season, which was set in 1978-79 by Kevin Keegan during his spell at Hamburg.
Meanwhile, it was a good day for Nelson's coach Nagelsmann, who recorded his 50th win in the Bundesliga, needing just 111 games to reach the milestone.
Nagelsmann will leave the club at the end of the season, having already agreed to join RB Leipzig.