Lascelles, Newcastle United's captain, limped out of Saturday's 3-1 FA Cup win over Luton Town at St James's Park.
The 24-year-old felt his groin during the third-round tie at St James's Park.
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Lascelles has helped steady the team since returning from injury a month ago.
And the defender – who was taken off as a precaution after Ayoze Perez put Newcastle ahead – is confident he will be fit in time to face Swansea at St James's Park.
Asked about his injury, Lascelles said: "I’m fine. I felt it go a little bit, and took no chances.
"I just wanted to make sure we won. I’m fine for next week. It’s nothing really, and I’ll be training Tuesday.
"I felt it a bit and didn’t want to make it worse. I think I made the right decision to come off and get it right for Swansea."
United are 13th in the Premier League table after taking seven points from their last four games.