Shoaib has been out of action since February with a knee injury and had an operation in Australia. He reported two days late for the camp in Lahore last week.
''Shoaib twisted his ankle while in practice. The team physio has had a look at it and he is doing the repair work,'' PCB Director Abbas Zaidi told Reuters.
Zaidi said Shoaib would rest for a few days but should be okay before the start of the main training camp next month.
''He remains with the rest of the players in the camp.'' The selectors have announced a preliminary squad of 21 players for the England tour with the touring squad due to be finalised on June 9.
Pakistan play four Tests and five One-day internationals in England.
The PCB has already said that while Shoaib is an important member of the team, he would have to play a couple of practice matches to prove his fitness for the tour.
Shoaib, 30, has taken 165 Test and 199 ODI wickets.
Pakistan captain Inzamam-ul-Haq and other leading players who played two exhibition matches in Saudi Arabia have all joined the conditioning camp.
Pacemen Mohammad Asif and Rana Naved, and all rounder Shahid Afridi, who play county cricket in England, have been allowed to skip the first phase of the camp.