Shelvey appeared to make contact after aiming a head-butt at Magpies defender Mathieu Debuchy before later completing the win with the Swans' third goal.
The midfielder had also earlier played a key role in his side's second, when his run ended with the ball ricocheting back off Debuchy and into the net, but it was his altercation with the Frenchman that was the talking point afterwards.
Asked if he had head-butted Debuchy, Shelvey told BT Sport: "That's what you think. Nowadays you can't do anything.
"I was trying to move to get out of the way. That's life at the end of the day."
Newcastle boss Alan Pardew was certain he should have seen red, though,. saying: "He shouldn't be on the pitch to score a third."
Pardew was also annoyed that his side, who were outplayed for large parts, were denied two penalty claims.
Ben Davies appeared to stop a goal-bound Loic Remy shot with his hand while the striker went down under pressure in his own box before Shelvey broke forward for his side's second.
Alan Pardew: "I'm still waiting for an explanation.
"The ball was going in the net and he (Davies) stuck an arm out. All our players have reacted. From the second they went up and scored. I'm aggrieved about the decisions.
"In all honesty though Swansea played terrific and we weren't good enough to cope at times. In the second half we pushed and when you push you need decisions to got your way - we've had two decisions go against us."
Source: Newcastle United Mad