Griffiths had starred for the Cowboys up to that point having scored two tries - one of those a fine individual effort right on half-time - to put his side in control but a clash of legs in an attempted tackle saw him left on the turf clutching his shin.

"I thought I'd broken it," he confessed.

The injury didn't stop the Cowboys running out 38-20 winners over Nyngan and advancing to the 2019 grand final, but it will remain a worry for the Wellington club this week.

Reports on Monday suggested Griffiths would be fit for Sunday's blockbuster grand final clash with Dubbo CYMS but he's one of a number of concerns within the squad.

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Tristan Lumley, after scoring the first try on Sunday, failed to finish the game due to a shoulder complaint while young half Rylee Blackhall also needed plenty of tape after twisting his ankle awkwardly in a tackle.

Those concerns come on top of the Steve Gordon's concussion suffered in the major semi-final and a Jack Kempston shoulder injury, while the Cowboys also lost winger CJ Ralph to injury late in the regular season.

But despite those worries the confidence and positive mood around the Cowboys is as strong as ever, with Griffiths' echoing coach Justin Toomey-White by saying the side has ticked one of the boxes by reaching this season's decider.

"It was great for the boys. It's good to get that win and now we'll see how we go against the Fishies," he said.

"We've got to prepare ourselves for the big game. It's what we've been chasing all year."

Griffiths played a major role in getting Wellington to a first grand final since 2010.

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After his side raced to an early 12-0 lead, Nyngan began to fight back and at 12-10 approaching half-time it was firmly in the balance.

But a Nyngan forward pass gave Wellington one last chance, and after a scrum 40m from the line the Cowboys shifted left to Griffiths.

He did the rest by slicing through between Tigers defenders Hammond Erepan and Jone Yacadrau before showing great strength and speed to get to the line.

"I thought I could back my ability and beat them man on man and I told the boys to pack the scrum and I'd have a crack at him," Griffiths said.