Should I be concerned or am I over reacting?

So me and my boyfriend have been together officially for 3 weeks. He went away on a works course last week anyway his home and he was on his phone and I saw he had a girls name on Snapchat that I didn’t recognise so I asked him and he said he spoke to her whilst he was on his course where he met her but they’d only been talking like general chitchat, he couldn’t show me because ovbs on Snapchat it’s photos. I said to him I could contact the girl and he was like ok do you think it’s cheating?