What do you think of me ignoring my co-worker?
Why would you intentionally ignore a co-worker?
He said sorry about the morning incident, I don't know yet what incident he was talking about
Co-workers are expected to keep an open line of discussion in order to be able to get their job done. If you ignore someone at work it'll cause tension in the workplace. This can lead to a slow down in production or even more hurt feelings.
Okay, I'll talk to him about it.
That's good that you are going to talk to him. That way you can figure out what the whole situation is about.