Would you forgive youre almost bf use tinder?

Hi, I would like to get some input for my situation with a (French) guy I met on Tinder two months ago. We are both early twenties and since meeting up discovered we have many things in common and our characters match well. Something rare to find.
After a couple of weeks we decided to be exclusive and both deleted the Tinder app. This is a massive step forward for him as he has never had a serious relationship and only ever had friends with benefits from the app.
As I take longer to warm up to a guy he has had a couple of insecurities where he felt I wasn't as invested in him as he was in me. But I have addressed these and I felt like everything was going amazingly, he agreed this and has even said those three words to me for a few weeks (although I'm not there yet). All until recently- he was at my place and saw a book which my ex made me containing photos of us kissing and also snapshots of our tinder accounts. I asked him not to look but he said it was fine and he wanted to see it. I insisted no to but he still opened it.
The next day I was due to fly on holiday for a week and stopped by his place to say bye. Whilst there his phone accidentally slid to the recently used tab and there was Tinder...He had downloaded it that morning. When i confronted him he started getting confused and said he felt insecure from last night and he got it that morning because he likes the thrill of matching but had no intention to meet with any of the girls. So my question is, what is your take on it? Is he unhappy in the relationship or does he just have a cheater personality? Does he get a last chance? Seems coincidental he downloaded it the day I fly out of town....

French + Tinder = stopped reading (are you even serious)

If you agreed to be exclusive but then he's back on a dating app, i would be a bit suspicious to be honest.

I'm very suspicious but he does claim he liked the thrill of matching and that was it.... but where do you draw the line in that case. From what I understand he was a total Man whore beforehand and his friends are a bad influence so maybe he made a mistake and he's ready to learn from it... sigh...

You should tell him you feel it's inappropriate and if it continues you might need to reconsider the relationship.

Depends how good the explanation is, but generally a leopard doesn't change its spots