Colvin was on crutches in the locker room after the game and told the Houston Chronicle that he didn't "feel very good at all."
"It sounds like he could possibly play again this year, but I'm not definitive about that right now," O'Brien said.
The Texans are already down a cornerback after placing Kevin Johnson (concussion) on injured reserve earlier in the season. Veteran cornerback Shareece Wright is likely to see more playing time in Colvin's absence. Houston is also hoping cornerback Kayvon Webster will be able to make his 2018 debut in Week 5 against the Cowboys. Webster is recovering from an Achilles injury he suffered last season and was finally able to practice in a limited capacity last week.
"I'll know better later in the week, but we should have a chance to see what Kayvon can do this week," O'Brien said.
O'Brien said the team will have to "see how it goes this week" with wide receiver Will Fuller, who did not play in the second half due to a hamstring injury.
"We just have to manage it and see where it's at," O'Brien said. "In a game like that, if I thought that he really could have gone doing the things we needed to, I would have played him, obviously. He's a great player. I just didn't think he could do all the things we needed him to do, so that's why we decided to sit him in the second half."
The Texans were also without running back Lamar Miller for the fourth quarter and overtime. O'Brien said his starting running back got "a little banged up" against the Colts but should be OK going forward.