The England captain was making his international return after missing the RBS 6 Nations with ligament damage in the same right knee he injured today.
Moody, who already had the knee heavily strapped, limped off the field after 61 minutes with the help of two medics and he was still hobbling after the match.
England manager Martin Johnson will finalise his 30-man World Cup squad on August 22, with the first match against Argentina in Dunedin on September 10.
But Moody insisted: "It was just a tweak to the knee. I am walking fine. It is nicely strapped up. We will see how it is in a couple of days."
England escaped lightly on the injury front compared to Wales, whose full-back Morgan Stoddart will miss the World Cup after suffering a broken leg.
After spending the best part of seven weeks in camp, England manager Martin Johnson felt the first of three warm-up fixtures was a productive exercise.
It was certainly far more productive than the equivalent fixture four years ago, when Wales sent a third team to Twickenham and were beaten 62-5.
England opened a 20-7 lead today with tries from James Haskell and debutant Manu Tuilagi but took their foot off Welsh throats when Johnson wanted them to press home the advantage.
Wales finished strongly with tries from Shane Williams and a second from George North, who added to his first-half score.
The Wales captain Sam Warburton felt England were "hanging on" at the end.
Johnson said: "It is what we wanted - to get out there and play a Test match. You get far more out of that than from the 60-pointers that occasionally happen.
"At 20-7 we needed to control the ball but we started to turn the ball over, then we invited them right back onto us. They nearly took that opportunity.
"We wanted to go and play it in the context of a proper game and win a Test match. We weren't going to treat it as a training game.
"I thought Jonny handled it very well. We got ourselves in a great position but we didn't finish it off."
Tuilagi, the powerful Leicester centre, marked his debut with a try under the posts.
"I feel fortunate that I am here and that I am playing for England," he said.
"I am very happy. Playing outside Jonny Wilkinson and Riki Flutey, guys that have been playing at the top level, was an honour."
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