The fullback will have scans to assess the severity of the injury.
Tomkins was again impressive yesterday and the team lost some structure in his absence, as Tui Lolohea moved to fullback and Ben Henry to centre.
"We didn't handle the changes as well as we could have," admitted Warriors coach Andrew McFadden. "We had different personnel [and] we didn't trust each other."
Meanwhile, concussion issues might dominate the agenda over the next few days, as Eels hooker Nathan Peats looked badly dazed as he was assisted from the field in the first half, only to return and complete the match.
"Yeah, I was surprised [he returned]" said McFadden. "He looked like he was pretty dazed."
Eels coach Brad Arthur defended the decision, saying he had full confidence in the judgement of his medical team.
"I was told he was good to go back out," said Arthur. "I have faith in our people.
"[The NRL] will see that we followed our processes."