Felton underwent an MRI on Sunday evening to determine the extend of the injury. The Knicks are listing him as day to day.
"It's swollen right now," Felton said. "It's a lot of pain, but we'll see what happens."
Felton said, if it were up to him, he'd play in the Knicks' next game on Wednesday against the Charlotte Bobcats. Felton said he could play with a bandage on his hand, if necessary.
If Felton is forced to sit, the Knicks could have just one healthy point guard available against Charlotte.
Veteran guard Jason Kidd has missed the Knicks' past four games and is listed as day to day due to lower back spasms.
Kidd, 39, hopes to return to the team sometime during their three-game road trip.
With Felton injured, Pablo Prigioni is the Knicks' lone healthy point guard.
Felton hurt his hand while trying to split a double team in the fourth quarter against the Suns. He said the pain was concentrated in his thumb, which was visibly swollen after the game.
"It got jammed," he said. "It hurts."
The 28-year-old Felton has been a vital piece for the Knicks (12-4) this season.
He scored 23 points on 10-for-17 shooting against Phoenix and added a team-high seven assists.
The Knicks are 3-1 without Kidd, thanks in part to Felton's steady play.
On the season, Felton is averaging 14.6 points and 6.7 assists per game while hitting 40.7 percent of his three-point attempts.
Ian Begley is a regular contributor to ESPNNewYork.com