Wells, who has recently been feeling discomfort in the area, was left out of last Saturday's match at Accrington Stanley as a precaution.
"It seems to settle down for a period and then suddenly flare back up again," Parkinson said when talking about Wells' current injury issue.
"On the whole, Nahki has been able to training pretty normally but it seems to catch when he goes to strike a ball - something which is obviously a huge part of his game.
"I didn't want to play him on Saturday (at Accrington Stanley) unless he was right in his mind to do so.
"We're now having it investigated thoroughly so we'll see what comes up."