The 31-year-old came on as a second-half substitute in the Magpies's 3-1 pre-season defeat to the Portuguese side, scoring his side's consolation goal before being forced off following a seemingly innocuous challenge.
He was reported to have left the stadium with bandages on his arm, and Pardew revealed that the centre-forward had been sent to hospital for X-rays.
"The most worrying thing to come out of the game is Shola," Pardew told The Times.
"It looks like he’s hurt his arm and he's going to have to go for an X-ray. We don't know how bad it is. Everybody else is fine. It's not really a position where we can pick up problems."
A prolonged absence for Ameobi would leave Newcastle with Yoan Gouffran and Adam Campbell as their only available striking options for their pre-season tour, with Papiss Cisse left at home amid a dispute with the club over their sponsorship arrangement with Wonga.
"I think it's fairly obvious," Pardew added.
"Papiss isn’t here and we're looking to strengthen that area. It hasn’t helped today that Shola has hurt his arm. We're really relying on Yoan Gouffran at the moment who isn't really operating in his best position in terms of (being) up there on his own. It isn't ideal. Hopefully we can get new players as soon as we can.
"The team's commitment to the cause was very good. Maybe we lacked a bit of aggression in our game.
"We were a bit passive I thought, but we were playing under fatigue there today - that's where we are in our fitness programme - and it showed. In the second half we put our fresher players on and that made a big difference. We could have got a draw in the end. It was three poor goals on our behalf."
Pardew has previously expressed an interest in Aston Villa's Darren Bent and Lyon forward Bafetimbi Gomis, with QPR's Loic Remy also thought to be a target.