Fears were high when Lukaku, who has been in prolific form leading up to the tournament, was hurt in a collision with Tunisia's Bilel Mohsni on Saturday.
Lukaku had to be withdrawn, with initial reports suggesting the problem could be serious enough to rule him out of the tournament.
However, the 21-year-old has now allayed such worries, insisting he will be fit for Belgium's opening fixture against Algeria next week.
"For the next few days I'll rest it," said Lukaku.
"I think that is the best option and I will definitely be ready for Algeria."
Belgium coach Marc Wilmots was similarly positive, adding: "It is a bruise. With intensive treatment for three to four days, it'll be okay."
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