<human>: My SO has been gone for 6 weeks and just came back for a visit. On the second day we were going to lunch and we were using his GPS to get there.

I was on my SO's phone and was looking at the apps he had open because we were using the GPS and the phone was kinda slow.

One of the apps he had open was Tinder, and I had only heard about it, I didn't really know what it was besides an app for dating and sex.

At first I didn't open it because I didn't want to. But then I though I'd better and see why he had it. I noticed that he cropped our one year anniversary picture of us together and had no mention of a SO or pictures of me. 

He saw that I found it and pulled over to talk to me about it, saying that nothing happened, it was a stupid decision and it didn't take him very long to realize that it was a mistake. 

I believe him because I love him. But he's lost my trust, what if something had happened? I didn't read the conversations on the app so I don't really know. 

What should we do to regain some trust?

Summarize the given text in a few sentences.
<bot>: My SO created a tinder account because he was feeling lonely after moving a province away and I'd like some advice on how to regain trust in our relationship has