Landskrona Bois won the match in the Superettan 3-1 and Norrköping suffered their second straight loss.
Nyman, 33, tied the score 1-1 in first-half stoppage time, but was forced to leave the field shortly after halftime, writes Aftonbladet.
The veteran attacker clashed with centre-back Andreas Murbeck and was left sitting before slowly walking off the field. Nyman suffered a concussion before the season and was forced to rest for a few weeks.
After Nyman left, Landskrona went on to win 3-1.
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