The Three Lions captain was in pain during the second half of the 6-2 victory over Iran in the opening match of Group B on Monday following a challenge from Morteza Pouraliganji.
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Despite staying on the pitch until the 75th minute, the Tottenham striker was eventually replaced by Callum Wilson.
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Kane was then pictured after the match with strapping around his right ankle.
England manager Gareth Southgate had played down fears over Kane's fitness following the thumping win over Iran.
Southgate said: "I think Harry's fine. It looked like a bad tackle but he carried on in the game. We took him off because we felt it was a moment in the game we could do that."
However, there are concerns he may have suffered worse damage than first feared.
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The 29-year-old will now undergo a scan to decide if the injury will keep him out of England's second match in Group B or for a longer period of time.
Against Iran, Kane did not score but played an influential role in the convincing win, setting up two of the six goals.
He won the Golden Boot at the last World Cup and is just two goals shy of Wayne Rooney's all-time England scoring record of 53.
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