With 7 minutes remaining, the Ulster player rifled the ball into the top corner from the edge of the D, ensuring that Ireland will compete in the 2018 competition.
Nelson also assisted his Ulster team mate Matthew Crookshanks for the opening goal of the morning on the 20 minute mark. Italy struck back not a minute sooner with a penalty stroke, converted by Matthias Malucchi, to draw the game level.
Italy soon grew into the game from here and they took the lead when Filippo Rubin beat Ben Bradley in the 53rd minute, making it 2-1.
From here, Ireland held onto the ball and Nelson stood up at the right time to deliver the crucial goal that relegated Italy.
Ireland’s girls team were up next but they fell short against a well-drilled Spanish side, with the game ending 6-1.
Spain attacked from the off, with Florencia Amundson looking menacing before she struck in the 13th minute. Lucia Abajo Saenz De Tejada followed shortly to make it 2-0.
The second half saw Abajo Saenz De Tejada grabbing her second goal of the afternoon before Michelle Carey kept her team in contention with a fine strike of her own, making it 3-1 with 18 minutes to play.
Spain put the game beyond doubt as Anna Barba, Patricia Alveraz and Alejandra Conill all added their names to the score board on the last day of action.
Germany were the overall winners in the boys championship as they saw off a spirited Dutch side by 4-3. The girls final saw the same match up, with Netherlands comprehensively beating Germany 2-0 at the Mardyke.
B Bradley; M Crookshanks; K Marshall; D Power; M Samuel; C Robson; M Nelson; G Sarratt; D Rae; C Empey; S McCabe.
H MacMahon; B Walker; A Tinney; D Jennings; A O’Hare; D Lynch.
E Buckley; N Carey; K Burns; E Curran; J McMaster; H McLoughlin; S Kelly; H Irwin; G McLoughlin; E Getty; K Edgar.
E Murphy; M Barry; N Carey; A Doyle; F McDermott; R Burns; R Henderson.