He almost cheated, so will he?

So I got on my boyfriends instagram and noticed where this girl had messaged him telling him not to be a stranger and asking what time he works. So he tells her he works until 4:30 but he gets laid off the rest of the week so if she wanted to meet up they'd have to do it the next day. However, she didn't reply until a while later and said sorry she fell asleep and he never responded back or met up with her.

So I ask him about it and get him to admit that he met her on tinder a few years ago and they had slept together, but he had her phone number blocked because he knew she would cause problems. He was just going to meet with her to see what she had to say.

He apologized and told me if he was trying to be sneaky and cheat on me I wouldn't know his passwords, he would've deleted the messages, and that if he wanted to sleep with her he would've chosen to meet her at her house, not a gas station (even though he never said in the messages that's where they were supposed to meet, he just assumes it's implied I guess).

He apologized and everything and told me he understands why I am hurt about it and blocked her on instagram too. But I'm afraid this is a red flag? Do you all think his intentions were bad, or that he might try to cheat in the future? We've been together for over a year and this is the first time something like this has happened.
He almost cheated, so will he?
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