Swann was hit on his bowling arm while batting on Monday on the second day of the four-day match.
What made matters worse was the fact it was the same arm which needed an operation on his elbow earlier this year.
But having taken five for 68 against Essex, the 34-year-old was feeling chipper.
"The arm's great," he told Sky Sports. "Obviously I was a bit worried at first when I got hit - I'm not used to getting smashed by rockets.
"But after a day off the field, watching our boys toil hard, I decided that it was time to get out there."
It was a welcome stint for the Nottinghamshire bowler, who said he needed some match practice.
"Having not played much in the Champions Trophy, and then missing out on the first innings here after getting whacked on the arm, I was very keen to get at least 20 overs under my belt," he said.
"Thankfully I managed to do that today (Wednesday), and to pick up a few wickets is always nice. The more you do something, the better you get at it.
"With the first Test at Trent Bridge next week, it was important I felt good about my game - and I do at the minute."
England coach Andy Flower said it was a relief to see a crucial part of his attack playing freely after Monday's scare, particularly with the first Ashes Test only a week away.
"There were great concerns about him. We thought he might have cracked his ulna (one of the two bones in the forearm)," said Flower.
"Luckily it wasn't the case, but it was badly swollen - not only when he was batting but afterwards.
"For a couple of hours, we thought he might have been missing (from the start of the Ashes) - which would have been a serious blow - but it would have given someone else a better chance.
"If something had been cracked, he wouldn't have been able to carry on batting.
"When he came in I was surprised by how swollen it was.
"I was also surprised by how well he played the fast bowler - after getting hit that badly, he fought it out there and didn't come off and get it seen to.
"It's a good example of his resilience. Because he's a jokey sort of guy, we forget he is quite a tough competitor as well."
Flower also received a boost regarding Stuart Broad, who had a cortisone injection in his sore right shoulder, an injury that ruled him out of the Essex match.
"He should be okay," said Flower. "He could not have played this game. But we hope that's it for that problem."