The problem has seen the midfielder withdraw from the England Under-21 squad for the forthcoming games against San Marino and Lithuania.
Rams coach Paul Simpson hopes it is not too serious and has his fingers crossed that the 18-year-old will be available when Derby resume Sky Bet Championship action after the international break at Watford on October 19.
"Apparently, it is something he started to feel maybe two or three weeks ago but he has been nursed through it," Simpson told the Derby Telegraph.
"It was obviously serious enough for the England doctors to send him back. We hope he will be fit for the next game against Watford."